MATERIALS TRANSACTIONS
New Arrival Alert : OFF

You can use this feature after you logged into the site.
Please click the button below.

Log in / Sign up
ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 48 (2007), No. 7

  • Microstructural Change by Friction Stir Processing in Zr-Al-Cu-Ni Bulk Metallic Glass

    pp. 1580-1583

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200770

    Microstructural change by friction stir processing (FSP) is examined in Zr-Al-Cu-Ni bulk metallic glass. The microstructure in the friction zone (FZ) exhibits an amorphous “band-like” structure, and a small number of nanoscale crystalline particles are observed along the “band-like” structure. The change in hardness with the microstructural change is examined and it is revealed that the hardness in FZ greatly increases although the volume fraction of crystalline phase is very limited. The increasing hardness is possibly explained from the combined effect of low temperature annealing during FSP and nano-size of crystalline particles.
  • Twin-Roll Strip Casting of Iron-Base Amorphous Alloys

    pp. 1584-1588

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200711

    In this study, three Fe-base amorphous alloys with quite different critical cooling rates were subjected to twin-roll strip casting to see the possibility of fabricating amorphous sheet by the same process. Continuous cooling transformation (CCT) diagrams of the alloys were calculated using the heterogeneous nucleation theory coupled with thermal data obtained during cooling to evaluate their critical cooling rates and glass forming abilities (GFAs). It shows that the GFAs calculated by CCT diagram are in agreement with the experimental results, while the well known empirical thermal parameters do not agree with the experimental results. Optimum twin-roll strip casting conditions have been determined based on the calculated critical cooling rates and the simulated thermal behavior of the sheet during twin-roll strip casting.
  • Microstructure and Mechanical Properties of Porous Zr55Cu30Al10Ni5 Bulk Metallic Glass Fabricated by Spark Plasma Sintering Process

    pp. 1589-1594

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200714

    We investigated the microstructure and mechanical properties of the porous Zr55Cu30Al10Ni5 bulk metallic glassy specimens fabricated by a spark plasma sintering process starting from the low sintering temperature, short holding time and rapid cooling. No crystallization within powder particles as well as at the interfaces between powder particles was identified by scanning and transmission electron microscopic observations. The sintered porous bulk metallic glassy specimens exhibited larger plastic strain and lower Young’s modulus than those of the as-cast alloy specimen. The increase in the plastic strain can be related to the pores in the sintered porous bulk glassy samples which generate multiple shear deformation events.
  • Preparation and Characterization of Dual-Phase Bulk Metallic Glasses through Powder Metallurgy Route

    pp. 1595-1599

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200791

    In the present study, amorphous Mg49Y15Cu36 and Ti50Cu28Ni15Sn7 alloy powders were synthesized separately by using a mechanical alloying technique. The dual-phase (Mg49Y15Cu36)100−x(Ti50Cu28Ni15Sn7)x (x=0, 10, 20, 30, 40, and 50 vol%) powders were prepared by mixing the corresponding amorphous powders. The amorphous dual-phase powders were then consolidated into bulk metallic glass (BMG) discs. The amorphization status of as-prepared powders and BMG discs was confirmed by X-ray diffraction and by using a differential scanning calorimeter. The microstructure of the BMG discs showed that the Ti50Cu28Ni15Sn7 phase is distributed homogeneously within the Mg49Y15Cu36 matrix. The (Mg49Y15Cu36)50(Ti50Cu28Ni15Sn7)50 BMG disc exhibited a relative density of 97.2% and its Vickers microhardness was 526±20 kg/mm2.
  • Ceramic Particulate Reinforced Zr55Cu30Al10Ni5 Metallic Glassy Matrix Composite Fabricated by Spark Plasma Sintering

    pp. 1600-1604

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200716

    Two-type sintered specimens of Zr55Cu30Al10Ni5 glassy alloy powder blended with and without 10 vol% ZrO2 ceramic powder, which had the similar relative density, were fabricated by a spark plasma sintering process in order to clarify the reinforced mechanical effect of ZrO2 particulates in the metallic glassy matrix composite. The structure, thermal stability and mechanical properties of the two-type sintered specimens were investigated. Two-type sintered specimens as well as original metallic glassy powder exhibited similar thermal stability. No crystallization of the metallic glassy matrix was demonstrated during the spark plasma sintering process. The plastic ductility of the sintered Zr55Cu30Al10Ni5 glassy matrix composite was enhanced by adding the ZrO2 particulates into the metallic glassy alloy. The improvement was originated from the structural inhomogeneity caused by the micro particles inclusion.
  • Fabrication of Bulk Metallic Glass Sheet in Cu-47 at% Zr Alloys by ARB and Heat Treatment

    pp. 1605-1609

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200735

    Pure Cu (99.96%) and pure Zr (99.8%) sheets were stacked and severely deformed up to equivalent strain of 16 by the accumulative roll bonding (ARB) process conducted at RT. The ARB processed sheets showed nanolamellar structure of Cu and Zr. The DSC curves of the ARB processed multi-layers exhibited characteristic exothermic peaks, which were similar to the previous results reported in a mechanical alloying study. When the ARB processed specimen was annealed at 400°C, at which the first exothermic peak appeared, most of the volume transformed into amorphous phase. The ARB processed and then 400°C annealed specimen showed obvious glass transition. That is, there is a possibility to fabricate bulk metallic glass sheet through severe plastic deformation and thermally activated amorphization.
  • Development of Low Density Ca-Mg-Al-Based Bulk Metallic Glasses

    pp. 1610-1616

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200731

    Low density Ca-Mg-Al-based bulk metallic glasses containing additionally Cu and Zn, were produced by a copper mold casting method as wedge-shaped samples with thicknesses varying from 0.5 mm to 10 mm. The compositions of the alloys were selected using recently developed specific criteria for glass formation. A structural assessment using the efficient cluster packing model was applied and showed a good ability to represent these glasses. Thermal properties of the new metallic glasses, such as the glass transition, crystallization and melting temperatures, as well as heats of crystallization and melting are reported. The effect of the alloy composition on glass forming ability is discussed.
  • Effect of Purity and Superheating on the Glass-Forming Ability of Mg-Cu-Y Alloys by an Electromagnetic Vibration Method

    pp. 1617-1620

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200721

    It is known that cooling rate from the liquid state is an important factor for producing the bulk metallic glasses. However, almost no other factors such as electric and/or magnetic fields were investigated. The present authors have reported that the glass-forming ability of Mg-Cu-Y and Fe-Co-B-Si-Nb alloys is enhanced with increasing electromagnetic vibration force. The electromagnetic vibrations affect the increase of the cooling rate and the decrease in the number of crystal nuclei directly, but don’t affect the crystal growing rate. However, effects of the electromagnetic vibrations are not fully investigated so far. Thus, this study aims to investigate effect of the purity and superheating on the glass-forming ability of Mg-Cu-Y alloys by the electromagnetic vibration method. It was found that the glass-forming ability of Mg-Cu-Y alloys is sensitive to the purity of an Ar atmosphere under which the mother alloy is prepared. However, the glass-forming ability was enhanced by the electromagnetic vibrations even if the mother alloy was prepared under low purity Ar. The enhancement of the glass-forming ability by the electromagnetic vibrations in the liquid state was decreased with the increase of superheating. These results support the presumption that disappearance or decrement of the clusters by the electromagnetic vibrations applied to the liquid state causes suppression of crystal nucleation.
  • Development of Mg Based Amorphous Alloys with Higher Amounts of Rare Earth Elements

    pp. 1621-1625

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200724

    There have been many alloy systems for the Mg based bulk metallic glasses (BMGs), with the previous optimum composition being Mg65Cu25Y10. In this study, new optimum alloy designs are made based on the theoretical model involving the electron per atom ea-related criterion and the recent model of optimum composition extension from the binary eutectic-pair criterion. Both models suggest that the optimum Mg based BMGs might possess a composition with a lower amount of Mg element. It follows that a series of Mg based BMGs with 50–65 at% Mg and 10–25 at% rare earth element are prepared. The glass forming ability, thermal characteristics, and mechanical performance are examined and discussed.
  • Glass-Forming Ability and Mechanical Properties of the Ternary Cu-Zr-Al and Quaternary Cu-Zr-Al-Ag Bulk Metallic Glasses

    pp. 1626-1630

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200704

    The effects of addition of Al and equivalent atomic ratio of Ag and Al on the glass-forming ability (GFA) of the Cu50Zr50 alloy are investigated. It is found that the alloy with the highest GFA is the Cu46Zr46Al8 alloy in ternary (Cu50Zr50)100−xAlx alloys, and the critical diameter is at least 8 mm. The simultaneous addition of Ag and Al is more effective to increase the glass-forming ability of the binary Cu50Zr50 alloy. The critical diameter of a glassy rod is 12 mm for the Cu42Zr42Al8Ag8 alloy. High stabilization of the supercooled liquid is the reason for high GFA of the Cu46Zr46Al8 and Cu42Zr42Al8Ag8 alloys. Both glassy alloys exhibited high fracture strength above 1960 MPa, but no distinct plastic strain is seen. There is no evident difference in the mechanical properties of the as-cast Cu42Zr42Al8Ag8 glassy rods with different diameters.
  • Phase Equilibrium in the Cu–Ti–Zr System at 800°C

    pp. 1631-1634

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200742

    The isothermal Cu–Ti–Zr phase diagram at 800°C was constructed by means of 36 equilibrated alloys. Electron microprobe analyses were used to determine the phase compositions and phase relationships. Most of the Cu–Zr binary intermetallic phases show a large Ti solubility and extend to the ternary region. CuTi2 and CuZr2 form a complete solid solution as a Cu(Ti,Zr)2 phase. One ternary phase, Cu2TiZr, formed at the central region. These phase relationships are quite different from the 703°C isotherm mainly determined by X-ray analysis.
  • Evaluation of the Glass-Forming Ability of Nb-Ni-Ti-Zr Quaternary Alloys Using the CALPHAD Approach

    pp. 1635-1638

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200736

    The glass-forming ability of Nb-Ni-Ti-Zr quaternary alloys has been evaluated by combining the Calculation of Phase Diagrams method with the Davies-Uhlmann kinetic approach. Time-temperature-transformation (TTT) curves were obtained for steady state nucleation for the calculations, which give the time required for the formation of detectable amounts of a crystalline phase from a supercooled liquid as a function of temperature. Then, the critical cooling rates for glass formation were calculated from the TTT curves. Among the input parameters for the calculation of the TTT curves, the driving force for crystallization of the crystalline phase was derived using the thermodynamic function of each phase formulated in previous studies. The calculations show that the critical cooling rates for Nb40−xyNi60TixZry alloys decrease with increasing Zr content up to 20 mol%Zr. In particular, the calculated values for the Nb10Ni60Ti10Zr20 and Nb5Ni60Ti15Zr20 alloys were around 100 K/s.
  • Phase Separation and Crystallization in Cu-Zr Metallic Glasses

    pp. 1639-1643

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200708

    The structural behavior of rapidly quenched Cu-Zr amorphous alloys was analyzed. High energy X-ray diffraction patterns and atomic pair correlation functions exhibit monotonic changes with composition. The experimental results can be well described by a solid solution-like replacement of Cu and Zr atoms in the whole composition range. No indications are observed that would support the existence of phase separation in the supercooled liquid state of the binary Cu-Zr alloys. For Cu60Zr30Ti10 and Cu60Zr20Ti20 bulk metallic glasses the formation of ultrafine nanostructures are proven upon heating. The transformation starts below the glass transition temperature. Phase separation in Cu-Zr-Ti bulk metallic glasses is related to primary crystallization.
  • Electron Irradiation Induced Crystallization Behavior in Zr66.7M33.3 (M=Cu, Ni, Pd) Metallic Glasses

    pp. 1644-1650

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200703

    The difference in electron irradiation induced crystallization behavior of melt-spun amorphous phase among Zr66.7M33.3 (M=Cu, Ni and Pd) alloys was investigated. An amorphous phase was unstable under electron irradiation and the irradiation induced crystallization of the amorphous phase occurred in the three alloys. The phase selection of electron irradiation induced crystallization in Zr66.7Pd33.3 was obviously different from that in Zr66.7Cu33.3 and Zr66.7Ni33.3, while there was no significant difference between the latter two. The origin of the unique phase selection in Zr66.7Pd33.3 alloy was discussed based on the database of electron irradiation induced crystallization in Zr-based alloys.
  • Electron Irradiation Induced Crystal-to-Amorphous-to-Crystal Transition in Some Metallic Glasses

    pp. 1651-1658

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200701

    Electron irradiation induced crystal-to-amorphous-to-crystal (C-A-C) transition in metallic glasses was investigated in various metallic glasses among binary Zr-based, ternary Fe-Nd-B and Fe-Zr-B alloys. In situ observation of the TEM microstructures and corresponding SAD patterns was performed by ultra high-voltage electron microscope (UHVEM). The origin of amorphization, crystallization and C-A-C transition was discussed based on the temperature-Gibbs free energy diagram.
  • Electron Irradiation Induced Phase Transformation in Fe-Nd-B Alloys

    pp. 1659-1664

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200702

    The effect of electron irradiation on the phase transformation in binary Fe-Nd and ternary Fe-Nd-B alloys was investigated. Electron irradiation induced nano-crystallization of amorphous-to-crystal (A-C) transition was observed in several Fe-Nd-B metallic glasses. In Nd2Fe14B compound, solid-state amorphization (SSA) of crystal-to-amorphous (C-A) transition occurred under electron irradiation. With further irradiation, the amorphous phase obtained by SSA transformed to the nano-crystalline phase through irradiation induced crystallization, resulting in crystal-to-amorphous-to-crystal (C-A-C) transition. A-C, C-A and C-A-C transition were also observed in some ternary Fe-Nd-B and binary Fe-Nd alloys. The electron irradiation technique is effective for the formation and control of nano-crystalline structure through A-C transition of amorphous phase and/or C-A-C transition of metallic compounds.
  • Nanocrystalline Transformation and Inverse Transformation in Metallic Glasses Induced by Electropulsing

    pp. 1665-1670

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200726

    Electropulsing by means of discharge of a condenser with the decay time (τ) of ms causes the athermal crystallization of metallic glasses when the initial current density (id0) is higher than the threshold value (id0,c). It is indicated that the major local amorphous structures in Zr50Cu50 are the amorphous structures with the short range order (SRO) similar to crystalline cubic (c) ZrCu which is the equilibrium crystalline phase above 988 K, although the mixture of crystalline Zr2Cu and Zr7Cu10 is the equilibrium phase below 988 K. Electropulsing tests on Zr50Cu50, Zr50Cu40Al10 and Zr50Cu35Al10Ni5 metallic glasses indicate that the amorphous structures with SRO similar to cZrCu are the major local amorphous structures in these metallic glasses, and their volume fractions decrease in the order of Zr50Cu50, Zr50Cu40Al10 and Zr50Cu35Al10Ni5. The amount of the amorphous structures with SRO similar to cZrCu may govern the thermal stability of these metallic glasses. Further in Zr50Cu50 metallic glasses, the inverse transformation from the electropulsing-induced fine crystallites to the amorphous phase for subsequent electropulsing with increasing id0, and the Ostwald-ripening-like phenomenon under electropulsing were observed.
  • Estimation of Relative Glass Forming Abilities of Multicomponent Alloy Systems

    pp. 1671-1674

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200718

    A thermodynamic calculation scheme based on a CALPHAD method has been studied to evaluate the relative glass forming abilities (GFAs) of multicomponent alloy systems. The concept of the normalized driving force has been developed for estimation of the relative GFAs of different alloy systems. Driving forces of formation of crystalline phases under metastable supercooled liquid state have been calculated for different alloy systems to predict the possible crystalline phases and the maximum driving forces normalized by the respective melting temperatures are correlated with the experimentally obtained GFAs of the alloys. It shows that the estimated relative GFAs of different alloy systems based on the normalized driving forces agree well with the experimental results.
  • A Simple Model for Examining Composition Effects in Eutectic Nucleation

    pp. 1675-1679

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200778

    We present a simple thermodynamic calculation for a strongly partitioning eutectic system, to examine how the critical nucleus energy changes, depending upon assumptions of the chemical diffusion. The calculations show that for strongly partitioning systems, the maximum undercooling may occur at a composition significantly different than the eutectic composition, particularly if the rate of diffusion is slow in the undercooled state. These simple calculations emphasize the role that partitioning and composition may play in determining optimal compositions in metallic glass systems, which typically occur near (but not at) deep eutectic compositions.
  • The Influence of Similar Element Coexistence in (La-Ce)-Al-(Co-Cu) Bulk Metallic Glasses

    pp. 1680-1683

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200748

    In this paper, a pseudo-ternary (La0.5Ce0.5)65Al10Co25 alloy with high glass-forming ability (GFA), identified by the formation of glassy rods up to 12 mm in diameter by copper mold casting, was reported. Furthermore, according to the viewpoint that similar element coexistence can be beneficial to improve the GFA, Cu was chosen as the similar element to substitute for solute Co in (La0.5Ce0.5)65Al10(Co1−xCux)25 alloys (0≤x≤1). The influence of this substitution on thermal stability, melting and solidification behaviors of these metallic glasses was evaluated. The optimized (La0.5Ce0.5)65Al10(Co0.6Cu0.4)25 alloy with high reduced glass transition temperature (0.66) and the large nominal supercooled degree (114 K) can form the fully glassy rods up to at least 25 mm in diameter by tilt-pour casting.
  • Glass Forming Ability and Thermal Properties of the Mg-Based Amorphous Alloys with Dual Rare Earth Elements Addition

    pp. 1684-1688

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200738

    The Mg58Cu31Y11−xNdx (x=0∼11) amorphous alloy rods with 3∼10 mm in diameter were prepared by Cu-mold injection method. The XRD result reveals that these entire Mg58Cu31Y11−xNdx alloy rods exhibit a broaden diffraction pattern of amorphous phase. A clear Tg (glass transition temperature) and supercooled region (about 70 K) were revealed for all of those Mg58Cu31Y11−xNdx amorphous alloy rods. The single stage crystallization of the Mg58Cu31Y11 alloy was found to change into two stages crystallization when large amount of Nd element was added into this alloy. In parallel, the crystallization temperature (Tx) and supercooled region (ΔTx) present a decreasing trend with increasing Nd content. The highest γ value of 0.414 occurs at the alloy compositions of Mg58Cu31Y4Nd7 and Mg58Cu31Y6Nd5 in this alloy system. Therefore, suitable addition of Nd element can obviously increase the glass forming ability for the Mg58Cu31Y11−xNdx alloy system.
  • Comparison of Crystallization Process of Amorphous Zr2Ni Alloy and Metallic Zr2Cu Glass

    pp. 1689-1693

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200719

    Crystal nucleation and time evolution during isothermal annealing in amorphous Zr2Ni at several temperatures just below a crystallization temperature Tx and in supercooled liquid of metallic glass Zr2Cu are examined using a technique of differential thermal analysis. Time dependence of the fraction of crystallization at several temperatures is analyzed by the Johnson-Mehl-Avrami equation. The Avrami exponent is 3.0±0.2 for Zr2Ni and varies from about 3 to 7 for Zr2Cu with increasing temperature. It is suggested for Zr2Ni that the crystal growth at temperatures just below Tx is ruled by a short range diffusion process of constituent elements. The time evolution of crystallized fraction was not well scaled by the half of complete time for full crystallization.
  • Effects of P Content on Nanocrystalline Morphology Formed by FIB Irradiation in Ni-P Amorphous Alloy

    pp. 1694-1697

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200754

    We studied the effects of phosphorus (P) on the Ni nanocrystalline morphology of Ni-P amorphous alloy thin films subjected to focused ion beam (FIB) irradiation. The P contents in the amorphous alloys varied from 14 to 20 at%. The nanocrystals induced by FIB irradiation of Ni-20.2, 15.6, and 14.0 at%P amorphous alloys had a face-centered-crystal (f.c.c.) structure and showed unique crystallographic orientation relationships to the geometry of the focused ion beam, with {111}f.c.c. parallel to the irradiated plane and ⟨110⟩f.c.c. parallel to the direction of the projected ion beam, respectively. The Ni nanocrystals formed by FIB irradiation precipitated in the same manner as aggregates, and the average size of the Ni nanocrystals increased as the P content decreased. These results indicate that the P content does not affect the crystallographic orientation relationships but does influence precipitation distribution of the Ni nanocrystals.
  • Voronoi Analysis of the Structure of Ni-Zr-Al Ternary Metallic Glass

    pp. 1698-1702

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200750

    Ni-Zr metallic glasses have been recognized to be unstable in comparison with Cu-Zr metallic glasses. An analysis of Voronoi polyhedra in the RMC simulations based on the diffraction data could characterize the atomic configurations around Ni and Cu atoms. The polyhedra around Ni atoms are dominated by trigonal prism-like, Archimedian antiprism-like, and similar polyhedra. In contrast, icosahedron-like polyhedra are preferred for Cu. The Ni-Zr glasses have been reported to stabilize by adding Al. Therefore, in this work, the analysis of Voronoi polyhedra around Ni, Zr and Al atoms for Ni25Zr60Al15 ternary metallic glass was carried out in order to clarify the difference between the atomic structures for the binary and ternary metallic glasses. Trigonal prism-like, Archimedian antiprism-like and similar polyhedra, which are dominated in the Ni-Zr metallic glasses, decreased in number by adding Al to the Ni-Zr system. On the contrary, the number of icosahedron-like polyhedra was found to increase. The results apparently indicate that the addition of Al into Ni-Zr binary system promote the formation of icosahedron-like polyhedra in the structure. Therefore, from these results, we can easily recognize that icosahedron-like polyhedra play an important role to stabilize the structure of metallic glasses.
  • Local Structure Study in Zr-Based Metallic Glasses

    pp. 1703-1707

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200753

    The local structure in the glassy state is investigated in the Zr80Pt20 and Zr70Cu30 binary and Zr70Al10Ni20 ternary alloys in correlation with the quasicrystalline (QC) phase formation. The Zr80Pt20 alloy has a high QC-forming ability. It is easily formed in the as-quenched state with a considerably low cooling rate or by annealing the glassy alloy. The radial distribution function (RDF) and extended X-ray absorption fine structure (EXAFS) analysis clearly indicate the existence of icosahedral local structure around Pt atom. The Zr70Cu30 binary and Zr70Al10Ni20 ternary metallic glasses have a QC-forming ability by the addition of a very small amount of noble metals such as Pd. We can also investigate the icosahedral local structure in these alloys. These results are realized that the icosahedral local structure can be applied as a dominant local atomic configuration in the supercooled liquid and/or glassy states in the QC-forming metallic glasses.
  • Precise Measurement of Density in the Isothermal Relaxation Processes of Pd42.5Cu30Ni7.5P20 and Zr50Cu40Al10 Glasses

    pp. 1708-1710

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200772

    The isothermal relaxation processes of bulk Zr50Cu40Al10 and Pd42.5Cu30Ni7.5P20 glasses were examined by density reduction associated with relaxation. Density experiments were carried out by buoyancy method at room temperature. The isothermal relaxation curves were best fitted by a stretched exponential function with a Kohlrausch exponent less than unity. Based on free volume model, the reduced free volume xfas=0.0355 and flow defect concentration Cfas=5.80×10−13 in as-quenched state was obtained for Pd42.5Cu30Ni7.5P20 glass. However, the temperature at which the free volume started to deviate from equilibrium concentration on cooling of the melt was not in accordance with calorimetric glass transition temperature.
  • Cluster Expansion Approach for Relative Stability among Different Atomic Structures in Alloys: an Approach from a Dilute Limit

    pp. 1711-1716

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200751

    We demonstrate the ability of our cluster expansion approach (CEA) for cohesive energies of alloys, which allows one to study the chemical trends of the relative stability of different atomic structures of alloys, as an example, X dependence of the atomic structures of Al-rich AlX (X = Sc-Zn) alloys, including ordered structures (L12(Al3Sc), DO22 (Al3V)), a Mackay icosahedron (a local structure in the Al80Mn20 quasicrystal), and precipitate shapes in decomposition phases (Al1−cCuc, Al1−cZnc; c<0.05). All the terms in the CEA for Al-rich AlX alloy can be determined uniquely and successively from low-order to high-order by using the total energies of isolated Al and X atoms, pure Al and X metals, and X impurities in Al metal. The total energies of impurity systems are calculated accurately by using the all-electron full-potential Korringa-Kohn-Rostoker (FPKKR) Green’s function method, combined with the density-functional theory in the generalized-gradient approximation (GGA). We show: (1) the binding energies of X (X = Cu, Zn) impurities in Al are reproduced very well by the CEA including two- and three-body interaction energies of X impurities; (2) the chemical trends of structural stability among ordered structures (L12, DO22, DO23) of Al3X (X = Sc, Ti, V), being determined by use of the screened-FPKKR and GGA band-structure calculations, are reproduced by the CEA including only two-body (X-X) interaction energies in Al.
  • Thermal Stability and Mechanical Properties of Spray-Formed and Melt-Spun Al89La6Ni5 Metallic Glass Matrix Composites

    pp. 1717-1721

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200767

    A spray-formed Al89La6Ni5 metallic glass matrix composite plate was obtained in thickness of 1 mm and diameter of 200 mm, comprising over 64% primary crystals (e.g. Al11La3) uniformly dispersed in the glass matrix. The microstructure can not be achieved by annealing corresponding amorphous precursor. The crystals existing in the glass matrix were found to increase the hardness of the composite. Through nanoindentation test, the hardness and modulus of the composite at ambient temperature were found superior than its amorphous ribbon counterpart. The hardness of the composite was estimated with the rule of mixture from the constituents to be 4.4 GPa, which agreed well with the nanoindentation results. From loss modulus measurement and TMA test at elevated temperatures, a weak Tg signal in the range of 213–240°C was revealed in the as-spray-formed composite. Furthermore, the dimension shrinkage of the composite was only 0.5% during the TMA test, which is much smaller than that of amorphous ribbon counterpart by up to 20%. The enhanced hardness by constituent second phases and the dimension stability of the composite are associated with their inherent microstructure, the primary crystals in particular.
  • Structural Relaxation and Crystallization of a Zr44Ti11Cu9.8Ni10.2Be25 Bulk Metallic Glass

    pp. 1722-1728

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200747

    The influence of annealing on the structural changes and the room temperature mechanical properties of a Zr44Ti11Cu9.8Ni10.2Be25 bulk metallic glass has been investigated. The structural evolution upon relaxation or crystallization after annealing at a temperature within the supercooled liquid region was studied by thermal analysis, x-ray diffraction, transmission electron microscopy, extended x-ray absorption fine structure and dilatometer measurements. The effects of structural relaxation and nanocrystallization on the mechanical properties were also examined by hardness and compression tests using specimens annealed for various times. The apparent disappearance of plastic strain was found to be due to embrittlement induced by considerable crystallization of the amorphous phase.
  • Atomic Dynamics in Metallic Liquids and Glasses

    pp. 1729-1733

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200763

    How atoms move in metallic glasses and liquids is an important question in discussing atomic transport, glass formation, structural relaxation and other properties of metallic glasses. While the concept of free-volume has long been used in describing atomic transport, computer simulations and isotope measurements have shown that atomic transport occurs by a much more collective process than assumed in the free-volume theory. We introduce a new approach to describe the atomic dynamics in metallic glasses, in terms of local energy landscapes related to fluctuations in the topology of atomic connectivity. This approach may form the basis for a new paradigm for discussing the structure-properties relationship in metallic glasses.
  • Ab-Initio Data for Interatomic Interactions in Zr-Rich ZrX (X=Sc-Cu) Alloys and Stability of Icosahedron-Like Zr13−nCun (n=3, 4) Clusters in Zr70Cu30 Metallic Glass

    pp. 1734-1738

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200743

    We give ab-initio data for the study of the stability of the atomic structures of Zr-rich ZrX (X=Sc-Cu) alloys, such as the cohesive energies and equilibrium Wigner-Seitz radii of elemental metals X (X=Sc-Cu, Zr-Ag) and X-X (X=Sc-Cu) interaction energies in Zr. The calculations are based on the density functional thoery in the generalized gradient approximation and employ the full-potential Korringa-Kohn-Rostoker Green’s function method. Using the calculated results, we elucidate the fundamental features of interatomic interactions of Zr-rich ZrX alloys. Especially, we found that the pair interaction of Cu impurities in Zr becomes strongly attractive around the interatomic distance of 0.45∼0.46 nm. It is shown that this interaction may be important for the stability of icosahedron-like local atomic structures of Zr10Cu3 and Zr9Cu4 clusters in the Zr70Cu30 bulk metallic glass, being proposed experimentally. We also found that the atomic structure of an isolated Zr10X3 cluster transforms from the hcp structure (initial state) to an icosahedron-like structure (final state) for X=Cu, but not for X=Ni.
  • Topological Instability as a Criterion for Design and Selection of Easy Glass-Former Compositions in Cu-Zr Based Systems

    pp. 1739-1742

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200745

    In the present work we propose a new approach for predicting the best glass-former composition(s) in multi-component metallic glasses. By applying the λ criterion, a topological instability criterion proposed to predict the crystallisation behaviour of Al-based systems, we show that it is also successfully possible to reproduce compositional ranges where binary and ternary bulk metallic glasses (BMGs) have recently been obtained. Our results indicate that the good glass-former composition(s) lie(s) within fields of mutual and simultaneous topological instability of all the crystalline phases competing with glassy phase.
  • Microindentation of a Zr57Ti5Cu20Ni8Al10 Bulk Metallic Glass

    pp. 1743-1747

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200733

    Using microindentation technique, the indentation behavior of a Zr57Ti5Cu20Ni8Al10 bulk-metallic glass is studied over a range of the indentation load from 200 mN to 5000 mN. For the indentation load larger than 1000 mN, the indentation load-depth curves during unloading display three regions, a) a fast unloading phase at the onset of unloading, b) a linear phase at which the indentation load is proportional to the indentation depth, and c) a slow unloading phase after the linear phase. The size of the linear region increases with the increase in the indentation load, and the slope is independent of the indentation load. The indentation hardness decreases slightly with the increase in the indentation load. The plastic energy dissipated in an indentation cycle is proportional to the 3/2 power of the indentation load. The effect of the indentation loading rate on the indentation behavior is discussed.
  • The Influence of Viscous Flow Deformation on the Thermal Stability and Hardness of ZrCuAlNi Bulk Glassy Alloy

    pp. 1748-1751

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200712

    We investigated the thermal stability and hardness of a Zr55Cu30Al10Ni5 bulk glassy alloy after isothermal viscous flow deformation in the supercooled liquid region. The influence of deformation temperature, holding time and initial strain rate on the thermal stability and hardness of a Zr55Cu30Al10Ni5 bulk glassy alloy subjected to the high temperature compression test was examined by differential scanning calorimetry (DSC) and with a Vickers micro-hardness tester. The results showed that the incubation time for isothermal annealing crystallization reduced during the viscous flow deformation. Thermal stability of supercooled liquid decreased after viscous flow deformation. As the deformation temperature increased, the SCL region decreases. At lower temperatures below 713 K the structural relaxation occurred, resulting in a slight increase in hardness. The crystallization at higher temperatures of over 723 K caused a rapid increase in hardness. The supercooled liquid region decreased and the hardness increased with increasing deformation time. Higher strain rate resulted in larger deformation in the same deformation time, and had slight influence on the thermal stability and hardness of the Zr55Cu30Al10Ni5 glassy alloy. When the Zr55Cu30Al10Ni5 bulk glassy alloy was compressed for 300 s with an initial strain rate of 3.3×10−3 s−1 at the temperatures of 723 K, nanocrystallization occurred, and the grain size was evaluated to be smaller than 5 nm.
  • Temperature-Dependent Mechanical Property of Zr-Based Metallic Glasses

    pp. 1752-1754

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200757

    The compression tests were conducted on four Zr-based bulk metallic glasses (BMGs) with different Nb contents. The results show that the addition of few percent Nb did not change the mechanical property. At 77 K, the strength increased notably without embrittlement. Furthermore, it is suggested that the normalized strength changes linearly with the normalized temperature. Current results provided important evidences that BMGs have a great application perspective at cryogenic temperatures. In addition, it is found that at ambient temperature, the BMGs do not exhibit strain rate sensitivity. However, the strength is dependent on the strain rate at high and cryogenic temperatures.
  • Internal Friction of Nitrogen-Doped Zr-Based Glassy Composite Alloy

    pp. 1755-1758

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200759

    Internal friction of Zr-based glassy composite alloys containing dispersed-ZrN particles, which were prepared by a powder compact melting and liquid-quenching process using Zr-Al-Ni-Cu glassy alloy and AlN powders as the starting materials, has been investigated using a reed method over the temperature range of ∼90–350 K. It should be noted that a broad multi-composed peak was observed around 260 K. The peak internal friction was about 3×10−3. It was also noteworthy that the so-called ΔM effect of the Young’s modulus in its temperature dependence was observed. In addition, the internal friction at the peak temperature depended little on the strain amplitude in the range of about ∼1×10−6–∼2×10−4. These results indicate that the observed internal friction peak is related to the relaxation process. Since the hydrogen content in the sample was very low (0.24 at%H), the observed internal friction peak is suggested to be induced by the interstitially doped nitrogen in the glassy phase.
  • Characterization of Shear Banding in La-Based Bulk Metallic Glasses through Indentation

    pp. 1759-1764

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200761

    La64Al14(Cu,Ni)22, La63.1Al15.2(Cu,Ni)21.7, La57.6Al17.5(Cu,Ni)24.9, and La55Al25Cu10Ni5Co5 bulk metallic glasses (BMGs) with low glass transition temperature (Tg) were prepared by copper-mould casting method. The homologous temperature (the ratio of room temperature to Tg) of the four BMGs ranges from 0.64 to 0.73. Plastic deformation behavior of the BMGs at various loading rates was studied by nanoindentation. The results showed that the loading rate dependency of serrated flow, which is related to the nucleation and propagation of shear bands, depends strongly on the homologous temperature. The alloys with relatively high homologous temperature exhibit an increase in flow serration with increasing loading rate, whereas, the alloys with low homologous temperature exhibit prominent serrations at low rates. No distinct shear band is observed around the indents for all alloys after nanoindentation at all the studied loading rates. Alternately, shear band pattern are characterized through macro-indentation, which shows that shear band spacing decreases with the increase of the homologous temperature.
  • Influence of Indenter Geometry on the Deformation Behavior of Zr60Cu30Al10 Bulk Metallic Glass during Nanoindentation

    pp. 1765-1769

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200752

    As a first step in examining a new aspect of inhomogeneous plastic flow in bulk metallic glasses (BMGs) during nanoindentation, a series of nanoindentation experiments were performed on Zr60Cu30Al10 BMG with two pyramidal indenters (Berkovich and cube-corner indenters) having different centreline-to-face angle. It was revealed that the indenter angle can be a new controllable factor affecting the serrated flow behaviour of the BMG during nanoindentation, since a sharper cube-corner indenter induces different stress field under the contact from Berkovich indenter typically used. Results are discussed in terms of preliminary ideas for improving analysis of the shear-band-ruled deformation behaviours in the BMG during nanoindentation.
  • Fatigue Crack Initiation and Small-Crack Propagation in Zr-Based Bulk Metallic Glass

    pp. 1770-1773

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200758

    Fatigue tests on Zr-based bulk metallic glass were conducted under fully reversed cyclic bending (R=−1), and the surfaces of the fatigued specimen were observed to elucidate the fatigue crack initiation mechanisms. The fracture surface was also observed to examine the crack propagation mechanism. In contrast to most brittle materials, the metallic glass showed fatigue behavior. Its fatigue strength was much lower than its tensile strength, and it had a fatigue limit. In the S-N curve, the number of cycles at the knee point was much lower than that for crystalline metals. The fatigue crack initiation process observed by atomic force microscopy (AFM) showed that cracks were initiated at the bottom of shear steps just after their formation.
  • Temperature, Strain and Strain Rate Dependence of Serrated Flow in Bulk Metallic Glasses

    pp. 1774-1780

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200782

    New findings on the inhomogeneous plastic deformation of bulk metallic glasses (BMGs) have shown a disappearance of serrated flow below a critical temperature or above a critical strain rate. This correlates with a change in the strain rate sensitivity (SRS) from negative to positive values, suggesting a change in the deformation mechanism. In addition, a change in the SRS correlating with the increase in the stress drop magnitude is observed with increasing strain. Results on the serration and flow dependence for the binary BMG Cu50Zr50 show close phenomenological similarities with the Portevin - Le Châtelier or dynamic strain aging effect known for crystalline solids. An alternative model for the appearance and disappearance of serrated flow based on the structural relaxation of the atomic configuration of shear transformation zones is described.
  • Effect of Structural Relaxation on Mechanical Behavior of a Zr-Based Bulk-Metallic Glass

    pp. 1781-1784

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200734

    Using the instrumented nanoindentation and differential-scanning calorimetry, the effect of the structural relaxation at the elevated temperature on the Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk-metallic glass was investigated. The structural relaxation did not exert a significant influence on the plastic-flow behavior. However, the relaxation enhanced both the hardness and elastic modulus substantially. The decrease in the structural relaxation enthalpy before the glass transition indicates that the relaxation reduced the free volume significantly. The increase in the hardness and elastic modulus is attributed to the reduction in the free volume that resulted from the relaxation.
  • Evaluation of Micro-Sized BMG Tensile Specimen Fabricated by Electrolytic Polishing Technique

    pp. 1785-1788

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200755

    An electrolytic polishing technique was used to fabricate micro-sized tensile specimens from two Zr55Al10Ni5Cu30 bulk metallic glass samples. One sample had a fully amorphous phase, while the other had dendrites with an average size of 33 μm within the amorphous matrix. A scanning electron microscope showed that specimens fabricated by electrolytic polishing had smooth surfaces. The specimens were then subjected to tensile tests at room temperature. The fully amorphous specimen had a fracture strength of 1,640 MPa. This specimen also showed slight plastic deformation after yielding, as well as vein patterns and smooth surface on the fracture surface. Multiple thin shear bands generated from a shear band were observed on the side surface of fractured specimen. The specimen containing dendrites was quite low in strength compared to the fully amorphous specimen, and had yield and fracture strengths of 460 and 600 MPa, respectively. The specimen containing dendrites also showed plastic deformation and work hardening after yielding, as well as vein patterns and a brittle fracture region on the fracture surface.
  • Bulk Glassy and Quasicrystalline (Zr65Al7.5Cu27.5)100−xTix Alloys and Their Mechanical Properties

    pp. 1789-1792

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200760

    The glass-forming ability (GFA) and thermal stability of (Zr65Al7.5Cu27.5)100−xTix (x=0∼15; in at%) alloys have been investigated. It was revealed that a certain amount of Ti addition could improve the GFA of Zr65Al7.5Cu27.5 alloy effectively. The best bulk metallic glass (BMG) forming composition was found at (Zr65Al7.5Cu27.5)93Ti7. Bulk glassy samples with diameter of 7 mm were made by means of copper mold casting. Further Ti additions deteriorated GFA and led to the precipitation of icosahedral phase, and 3 mm quasicrystalline cylinder was obtained at (Zr65Al7.5Cu27.5)90Ti10. Room temperature compression testing showed that the quasicrystalline alloy had a fracture strength of 1875 MPa, being 300 MPa larger than that of the (Zr65Al7.5Cu27.5)93Ti7 monolithic BMG.
  • A Model for the Fragility of Metallic Glass Forming Liquids

    pp. 1793-1796

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200737

    An expression for the temperature dependence of the viscosity and fragility is derived based on a simple model of the melt. According to the model, the fragility is determined by the relaxation of structural units that form the melt, and is described in terms of the bond strength, coordination number, and their fluctuations of the structural units. It is shown that the fragility of some metallic glass forming liquids such as Pd40Ni40P20, La55Al25Ni20 and Zr65Al10Ni10Cu15 are quite well reproduced by the model. The application of the theory to La55Al25Ni20 has revealed that the fluctuation in the bond strength between the structural units is about 6% and that the viscous flow occurs when the bonds in about 8 adjoining structural units are broken.
  • Mechanical Properties of the Hot-Pressed Amorphous Mg65Cu20Y10Ag5/NanoZrO2 Composite Alloy

    pp. 1797-1801

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200707

    Amorphous Mg65Cu20Y10Ag5/nano ZrO2 composite alloys are fabricated through mechanical alloying (MA) in the planetary mill, using amorphous matrix alloy prepared by melt spun and 3 vol% spherical nano-sized ZrO2 particles. The specimens were hot pressed in Ar atmosphere under the pressure of 700 MPa at the temperature of soft point which is determined by TMA (Thermo mechanical Analysis). The hot-pressed composite alloy can reach to a 96% density, the hardness of 315±10 in Hv scale, and the compressive strength of 690 MPa. In addition, the result of mechanical test revealed that the nano-sized ZrO2 dispersion can obviously increase hardness as well as toughness of the Mg based amorphous alloy. Moreover, after compression test at 426 K (sample has been deformed 60 vol%), the hardness of hot-pressed composite alloy dramatically increases to Hv 400±25. An image of shear band being stopped in front of the ZrO2 particle was found by the TEM observation. Base on these two evidences, suggests that the strength of amorphous Mg65Y10Cu20Ag5 with 3 vol% ZrO2 composite alloy could be potentially improved by healing its residue porosity with hot deformation method within the supercooled liquid temperature region.
  • Compression Behavior of Mg-Cu-Gd Bulk Metallic Glasses with Various Specimen Height to Diameter Ratios

    pp. 1802-1805

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200722

    The mechanical behavior of the Mg65Cu25Gd10 bulk metallic glasses (BMGs) in term of compression testing is reported in this study. Room-temperature compression tests are conducted on specimens with various height to diameter ratios (hd) from 2:1, 1:1, 1:2, to 1:4. The failure strength, deformation strain, and the fracture surface morphologies are seen to vary systematically in accordance with the specimen hd ratio. For specimens with hd of 2:1 or 1:1, the compression response is similar to those in most reports. In contrast, for specimens with lower hd ratios, especially at hd=1:4 (or 0.25), the shear band propagation appears to be constrained, resulting in the enhanced ductility. It suggests that different deformation mechanisms are operative for specimens with different hd ratios. The possible deformation mechanisms in specimens of different geometries are discussed.
  • Impact of Microstructural Inhomogenities on the Ductility of Bulk Metallic Glasses

    pp. 1806-1811

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200725

    To circumvent the limited ductility of bulk metallic glasses (BMGs), heterogeneous materials with glassy matrix and different type and length-scale of heterogeneities (micrometer-sized second phase particles or fibers, nanocrystals in a glassy matrix, phase separated regions, variations in short-range order by clustering) have been developed in order to control the mechanical properties. As example, recent results obtained for Cu- and Ti-base structurally imhomogeneous bulk metallic glasses will be presented. This type of clustered glasses is able to achieve high strength together with pronounced work hardening and large ductility by controlling the instabilities otherwise responsible for early failure. We emphasize the possibilities to manipulate such spatially inhomogeneous glassy structures based on martensitic alloys in favor of either strength and ductility, or a combination of both and also discuss the acquired ability to synthesize such M-glasses in bulk form through inexpensive processing routes.
  • Mechanical Properties and Microstructures of Composites of Ti-Based Metallic Glass and β–Ti

    pp. 1812-1815

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200756

    Microstructures and mechanical properties of Cu mold-cast Ti50Cu25Ni15Sn5Ta5 and Ti45Zr5Cu44Ni5Ta1 alloys were investigated by means of X-ray diffraction, electron microscopy and compressive testing. Ti50Cu25Ni15Sn5Ta5 alloys form microscopic composites consisting of Ti-based metallic glass as primary phase and β–Ti phases, while Ti45Zr5Cu44Ni5Ta1 alloys consisting of Ti-based metallic glass matrix and high density of nanocrystals dispersed in the matrix homogeneously. Ti50Cu25Ni15Sn5Ta5 bulk composite alloys showed 1.6% of plastic deformation and 2200 MPa of 0.2% of proof stress. The alloys also exhibited work hardening because of the presence of microscopic crystalline phases. Ti45Zr5Cu44Ni5Ta1 bulk alloys also deformed plastically after stress reached 2000 MPa without work hardening.
  • Free Volume Evolution in Metallic Glasses Subjected to Mechanical Deformation

    pp. 1816-1821

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200785

    We define the Turnbull-Cohen free volume as the critical excess of the Voronoi volume of an atom less its core volume. Using molecular dynamics simulation we calculated the free volume change in two model binary metallic glasses undergoing tension and shear deformation. We show that the free volume change is an integral part of the deformation process; and the shear localization manifested as a shear band is directly related to the inhomogeneous distribution of the free volumes. Shear band formation may consist of two stages: the initial free volume production in the amorphous solids and the liquefaction of the regions with accumulated deformation strains. We show, for the first time, the formation of voids and the “vein” patterns on fracture surfaces at atomic scales; they are the combined result of the free volume change and loading and sample conditions.
  • Characterization of Zr-Cu Base Metallic Glasses by means of Hydrogen Internal Friction Peak

    pp. 1822-1827

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200727

    The hydrogen internal friction peak in Zr50-metallic glasses (Zr50Cu50, Zr50Cu40Al10 and Zr50Cu35Al10Ni5) was studied. The hydrogen internal friction peak was shifted exponentially to lower temperatures with increasing hydrogen concentration similarly to other Zr-Cu base metallic glasses reported in the literature. The peak height increased in proportion to the square-root of hydrogen concentration. These results were discussed in the view point of the hydrogen induced structural relaxation in these metallic glasses.
  • Compression-Compression Fatigue and Fracture Behaviors of Zr50Al10Cu37Pd3 Bulk-Metallic Glass

    pp. 1828-1833

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200780

    The compression-compression fatigue and fracture behaviors were studied on the Zr50Al10Cu37Pd3 bulk-metallic glasses (BMGs) under a load control, employing an electrohydraulic machine, at a frequency of 10 Hz (using a sinusoidal waveform) with an R ratio of 10, where Rmin.⁄σmax.min. and σmax. are the applied minimum and maximum stresses, respectively). The obtained results were compared with those of the tension-tension fatigue tests. The life under the compression-compression fatigue was improved significantly. However the fatigue-endurance limits in two different stress states are comparable. The fracture morphology and the specimen surfaces were observed. The possible different fracture mechanisms under two kinds of stresses were discussed.
  • Annealing Effects on Viscosity of Zr55Cu30Al10Ni5 Supercooled Liquids

    pp. 1834-1837

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200792

    Viscous flow behavior in supercooled liquid region of as-cast and annealed Zr55Cu30Al10Ni5 bulk metallic glasses has been examined by using a penetration viscometer under various heating rates of 20, 200 and 400°C/min. Applied load for the cylindrical-shaped penetration indenter with a diameter of 1 mm was varied from 0.049 N to 0.294 N. Viscosity was quite independent of these applied loads under the various heating conditions. When the sample was slowly heated at the rate of 20°C/min, viscosity exhibited relatively high values that may be mainly due to the skin effects of oxides on the sample surface. At the heating rate of 200°C/min and above, viscosity (η) largely decreased and tended to saturate. By annealing the bulk metallic glasses at 400°C, the density of the glasses increased, while the crystallization temperature (Tx), the viscosity and the activation energy for viscous flow in their soopercooled liquid decreased gradually with increasing the annealing time. The specific behaviour of viscosity has been explained by the formation of particles during annealing for relaxation.
  • Thermoplastic Deformation and Mechanical Properties of Zr-Based Bulk Metallic Glasses

    pp. 1838-1841

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200749

    The effect of heating and thermoplastic deformation on the fracture stress of Zr55Cu30Al10Ni5 and Zr60Cu25Al10Ni5 bulk metallic glass at room temperature (RT) was studied. These metallic glasses were easily crystallized by the influence of heating beyond their upper limit temperature of 685 K and 713 K, respectively. The fracture stress was maintained the strength of material as cast below these temperatures while it decreased easily by crystallization. It was possible to deform these materials below these temperatures. Their strength after thermoplastic deformation depended on the amount of strain, strain rate, and temperature during the deformation. The lower temperature and higher strain rate resulted in high strength after thermoplastic deformation at RT.
  • Low Temperature Elastic Properties of CuZrTi Bulk Metallic Glass

    pp. 1842-1845

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200764

    Temperature dependent elastic constants Cij(T) of Cu60Zr30Ti10 bulk metallic glass (BMG) have been studied using MHz frequency range electromagnetic acoustic resonance (EMAR) from 4.5 to 300 K. At ambient temperature, the BMG shows low shear/bulk modulus ratio (or equivalently high Poisson ratio) compared with that of corresponding crystalline state dues to the dense random packed glassy structure. Analysis of Cij(T) based on the Einstein type lattice vibration model revealed the notable softening in transverse mode acoustic phonons. This unusual vibrational property suggests the existence of liquid like weakly bonded region in the BMG.
  • Relations between the Thermal and Mechanical Properties of Cast Zr-TM-Al (TM: Cu, Ni, or Co) Bulk Glassy Alloys

    pp. 1846-1849

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200717

    Ternary Zr-TM-Al (TM: Cu, Ni or Co) bulk glassy alloys were fabricated to clarify the relations between the thermal and mechanical features. These alloy systems show the distinct ternary eutectic point, and a bulk glassy phase also forms around the ternary eutectic composition. We determine the 12 standard Zr-TM-Al bulk glassy alloys in this study. In the twelve standard Zr-TM-Al bulk glassy alloys, the glass-transition temperature has large positive correlation coefficient with Young’s modulus and Vickers hardness. The melting temperature has large negative correlation coefficient with Charpy impact value, fracture strain and volume change due to structural relaxation. Furthermore, in order to recognize the origin of ductility, Poisson’s ratio (metallic bond nature) and volume change (free volume) were also examined.
  • Corrosion Properties of Ca Based Bulk Metallic Glasses

    pp. 1850-1854

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200732

    The corrosion properties of ternary (Ca65Mg15Zn20 and Ca50Mg20Cu30), quaternary (Ca55Mg18Zn11Cu16), and quinternary (Ca55Mg15Al10Zn15Cu5) amorphous alloys were evaluated using static aqueous submersion at room temperature. Ca-Mg-Zn and Ca-Mg-Cu alloy systems experienced destructive corrosion reactions. Ca-Mg-Zn-Cu and Ca-Mg-Zn-Cu-Al based amorphous alloys demonstrated positive corrosion properties, forming corrosion films up to 23 μm thick in the quaternary alloy and 11 μm thick in the quinternary composition. Corrosion products were evaluated using X-ray diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS).
  • Corrosion Behavior of a Ti-Based Bulk Metallic Glass and Its Crystalline Alloys

    pp. 1855-1858

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200713

    The structure, thermal stability and corrosion behavior of the Ti40Zr10Cu36Pd14 bulk metallic glass and its crystalline alloys have been investigated in this paper. The results of potentiodynamic polarization measurements revealed that the Ti-based bulk metallic glass and its crystalline counterparts examined were spontaneously passivated by anodic polarization with the passive current density about 10−2 A/m2. The higher corrosion resistance for the Ti-based bulk metallic glass and partly crystalline alloys was attributed to stable and protective passive films enriched with titanium and zirconium. The Ti40Zr10Cu36Pd14 bulk metallic glass and its partial crystalline alloys produced recently without toxic elements are expected to be applied as biomaterials.
  • Microstructure and Elasticity of Glassy Alloy Surface by Reactive and Inert Ion Implantation

    pp. 1859-1863

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200720

    Present work focuses on the structural change of Zr-Cu glassy film via penetration of different reactivity of N+ and Ar+ and its elasticity measurement. Amorphous Zr-30 at%Cu film has been synthesized by ion beam sputtering on Si substrate. Nitrogen implantation induced precipitation microstructure with (Zr-Cu) nitride and Cu phase in glassy matrix. Inert gas element of Ar+ makes voids structure inside of the film at the mean penetration depth of Ar+ as maintained glassy phase. Resultant microstructures due to penetrated ions strongly depend on their degree of chemical reactivity with constituents. Surface elasticity of modified structure have been evaluated from nano-indentation test and given the normalization treatment for measured Young’s modulus.
  • Air Oxidation of an Fe48Cr15C15Mo14B6Er2 Bulk Metallic Glass at 600–725°C

    pp. 1864-1869

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200723

    The oxidation behavior of an Fe48Cr15C15Mo14B6Er2 bulk metallic glass (Fe-BMG) was studied over the temperature range of 600–725°C in dry air. The oxidation kinetics of the glassy alloy followed a two-stage parabolic rate law at T≤650°C, while the single-stage linear rate was observed at higher temperatures (T≥675°C). The oxidation rates of the Fe-BMG at T≤625°C were much lower than those of the commercial 304 stainless steel (304 SS), revealing the excellent oxidation resistance of the amorphous alloy. A continuous, thin layer of chromium oxide (Cr2O3) containing some iron was formed at T≤650°C, while typical hump iron oxides intermixed with minor amounts of Cr2O3 and MoO2 were observed at T≥675°C. In addition, a substrate phase transformation from the amorphous structure to Fe-Cr and FeCrMo crystalline phases was detected after the oxidation. Very likely, the formation of the non-protective Fe3O4 and MoO2 breaks the scale integrity and allows the rapid cation/anion transportation, resulting in the fast linear-kinetics behavior of the Fe-BMG at T≥675°C.
  • Oxidation Behavior of Ca-Based Bulk Amorphous Materials

    pp. 1870-1878

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200744

    In this study, the room-temperature oxidation behaviors of three Ca-based bulk amorphous alloys, Ca65Mg15Zn20, Ca50Mg20Cu30, and Ca55Mg18Zn11Cu16, were examined under normal flowing laboratory air and compared with the oxidation behaviors of these alloys in the crystalline form under identical conditions. The degree of oxidation for alloys in the amorphous and crystalline conditions was investigated by periodically measuring the mass change over the oxidation time. From the results of the oxidation mass change, and oxide thickness measurements obtained from scanning-electron-microscopy (SEM) studies, it was determined that the Ca55Mg18Zn11Cu16 BMG possessed the most favorable oxidation resistance, followed closely by the Ca50Mg20Cu30 BMG, with the Ca65Mg15Zn20 BMG having the least favorable oxidation resistance. The trend in glass-forming abilities of the three compositions follows the same trend as the oxidation resistance in the three alloys. In all cases, the oxidation resistance of the amorphous alloys was superior to the oxidation resistance of the same alloys in the crystalline state.
  • Formation and Biocompatibility of Ni-Free Zr60Nb5Cu20Fe5Al10 Bulk Metallic Glass

    pp. 1879-1882

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MJ200730

    A Ni-free bulk metallic glass (BMG) of Zr60Nb5Cu20Fe5Al10 with a diameter of 3 mm was successfully prepared by copper mold casting. The structure and thermal stability of the BMG were studied by x-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). It is found that the BMG is apparently of a single amorphous structure and exhibits a wide supercooled liquid region of 101°C. A static-state compression revealed that the BMG possesses a superior fracture strength of 1709 MP and extended plastic strain of 9.5%. The corrosion resistance of the BMG was examined by electrochemical polarization in phosphate buffered solution, which demonstrates that the BMG also exhibits an excellent corrosion resistance. Finally, the potential cytotoxicity of the Ni-free BMG was evaluated through cell culture followed by 3-(4,5-Dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide (MTT) assay and scanning electron microscope (SEM) observation. It is shown that the BMG exhibits a high cell viability and proliferation activity, and NIH/3T3 cells can closely adhere and well extend on the surfaces of the BMG alloy. The results indicate that the Ni-free Zr60Nb5Cu20Fe5Al10 BMG developed in the present work is promising for biomedical applications.
  • Ab-Initio Study of Hyperfine Structure of M7 (M=Li, Na, K, Cu and Ag) Clusters, Using All-Electron Mixed-Basis Method

    pp. 1883-1885

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.N-MRA2007857

    Within density functional theory, the geometrical properties and the hyperfine structure of 7-atom clusters, 7Li7, 23Na7, 39K7, 63Cu7 and 107Ag7 are investigated using the so-called all-electron mixed basis method. The calculations reveal that all the clusters have a pentagonal bipyramidal geometry with a D5h symmetry in which an unpaired electron occupies an a2′′ state. It turns out that, the unpaired electron in all the clusters is mostly distributed on the axial sites with a minor contributions at the pentagonal ring sites. The calculated spin distributions and the isotropic hyperfine parameters are in excellent agreement with the corresponding experimental data.
  • Quantitative Analysis of Texture Evolution of Direct Chill Cast and Continuous Cast AA 1100 Aluminum Alloys during Cold Rolling

    pp. 1886-1890

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2007023

    The hot bands of direct chill cast (DC) and continuous cast (CC) AA 1100 aluminum alloys were annealed at 454°C for 3 hours, and then cold rolled to different reductions. The texture of the cold rolled samples was measured by X-ray diffraction in order to compare the texture evolution of the DC and CC aluminum alloys during rolling. The texture volume fractions were calculated by an improved integration method. Mathematical formulae of the texture volume fractions and rolling true strain were established to simulate rolling texture evolution. The results show that the DC AA 1100 aluminum alloy exhibits a lower formation rate of the β fiber than the CC AA 1100 aluminum alloy.
  • Effect of Mo on Phase Separation in Fe-40 at% Cr Alloys Based on Numerical Solutions of the Cahn Hilliard Equation

    pp. 1891-1895

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2006335

    Effect of Mo on phase separation behavior of Cr in Fe-40 at%Cr-Mo ternary alloys was investigated with use of a model based on the Cahn-Hilliard eqaution. Simulation result indicates that the addition of a small amount of Mo to an Fe-40 at%Cr binary alloy was found to accelerate phase separation. With addition of small amount of Mo up to 5 at%, the rate of phase separtion concentration of Cr along the trajectory of its peak top increases with time. Mechanism of this acceleration behavior of Cr was analyzed by using a theory on asymptotic behavior of substitutional element in ternary alloy proposed by the present authors.
  • Crystal Nucleation Behavior Caused by Annealing of SiC Irradiated with Ne at Liquid Nitrogen Temperature or at 573 K

    pp. 1896-1900

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2007608

    Silicon carbide(SiC) TEM specimens were annealed, in-situ, at 1273 K for 30 minutes after amorphization with 30 keV Ne+ irradiation to the fluence of 1.9 or 2.3×1020Ne+/m2 at 573 K or liquid nitrogen temperature. The crystal nucleation and bubble coalescence accompanied by recrystallization were observed for both specimens subjected to the annealing after the irradiation to the fluence of 2.3×1020Ne+/m2 in both irradiation temperature cases. The Debye-Sherrer rings of the nucleated crystals well fitted the net pattern of the matrix, even though no ring corresponding to (200) of β-SiC appeared. No effect of the irradiation temperature occurred within the present experimental range. It appears that the concentration of implanted inert gas atoms played more important roll than the amorphous structure itself in the crystal nucleation behavior under the condition that the inert gas bubbles were formed in amorphous SiC.
  • Crushing Simulation of Foam-Filled Aluminium Tubes

    pp. 1901-1906

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2007071

    A numerical study is presented in this paper to investigate the energy absorption of foam-filled aluminium tubes during crushing. The post-buckling mode of the foam-tube structures has been successfully simulated. The predicted compressive load-displacement is in a good agreement with experimental results. The energy absorption ability of the composite structure due to plastic deformation in a crushing process is evaluated by comparison with the tube structure without foam. The results indicate that the energy absorption of a foam-filled tube structure is superior to the tube without foam. The influences of the friction and the geometric parameters of the structure on the energy absorption have also been investigated. Results from this study will assist automotive industry to design crashworthy components based on foam-filled tubes.
  • CO Oxidation Process on Pt-M(111) Alloys (M=Ru, Sn): An ab initio Study

    pp. 1907-1912

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.N-MRA2007858

    Direct Methanol Fuel Cell (DMFC) have attracted attention in recent years because they are very energy-efficient. However, there is a serious problem in that Pt, which is the usual anode electrocatalyst, is poisoned by CO. Therefore, it is very important to develop new materials for use as electrocatalysts that exhibit good tolerance to CO. The aim of this study is to examine the mechanism of H2O dissociation and of the CO+OH combination reactions in the CO oxidation process by calculating the adsorption energies and the activation barriers. In the case of Pt-Ru alloys, the activation barrier for the H2O dissociation reaction is almost the same as it is for pure Pt. The activation barrier for the CO+OH combination reaction on the Pt-Ru alloy is larger than that on pure Pt. Nevertheless, the adsorption energy of H2O is larger than that on pure Pt. On the other hand, the activation barrier and adsorption energies of H2O on the Pt-Sn alloy are very close to the corresponding values on pure Pt. Moreover, the activation barrier for the CO+OH combination reaction on the Pt-Sn alloy is lower than that on pure Pt.
  • The Effect of Hydroxy Ethyl Cellulose (HEC) and Chloride Ions on the Surface Morphology and Mechanical Characteristics during Copper Electrodeposition

    pp. 1913-1918

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2006326

    The effect of additives on the surface morphology and mechanical characteristics during copper electrodeposition on the polyimide(PI) film was investigated. Two kinds of additives such as hydroxy ethyl cellulose (HEC) and chloride ions were used in this study. Electrodeposition was carried out with the constant current density of 200 mA/cm2 for 68 seconds. Electrochemical experiments, in conjunction with SEM, XRD, AFM and four-point probe, were performed to characterize the morphology and mechanical characteristics of copper electrodeposited in the presence of the additives. The minimum surface roughness of copper deposit was obtained when deposited with 10 ppm of chloride ions. The minimum value of surface roughness (rms value) was 97.05 nm. And the optimum amount of additives to improve the electromigration resistance and ductility of the deposit was a combination of 1 ppm HEC and 10 ppm chloride ions.
  • Microstructure and Electrical Conductivity of Epitaxial BaRuO3 Thin Films Prepared on (001), (110) and (111) SrTiO3 Substrates by Laser Ablation

    pp. 1919-1923

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2007056

    BaRuO3 (BRO) thin films were prepared on SrTiO3 (STO) single crystal substrate by laser ablation, and their microstructures and the anisotropy of electrical conductivity were investigated. The (205) and (104) doubly oriented BRO thin film was grown epitaxially on (001) STO substrate. Epitaxial (110) and (009) BRO thin films were obtained on (110) and (111) STO substrates, respectively, at oxygen pressure of 13 Pa and substrate temperature of 973 K. Epitaxial (205) (104) BRO thin film had a tetragonal texture whereas (110) BRO thin film showed a faceted island texture. Epitaxial (009) BRO thin films had a smooth surface due to a good lattice consistency between (009) BRO plane and (111) STO plane, and exhibited the highest electrical conductivity of 1.1×105 S·m−1 among the (205) (104), (110) and (009) BRO thin films.
  • Effects of Electron Beam Irradiation on Charpy Impact Value of GFRP

    pp. 1924-1927

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2007050

    Glass fiber reinforced polymers GFRPs are increasingly being applied as structural materials with their advantages of light weight and high strength in the fields of aerospace engineering and rapid transport engineering. To strengthen the GFRPs, sheet electron beam (EB) irradiation under low potential has been performed homogeneously. Effects of EB-irradiation on Charpy impact value of GFRPs have been studied. The irradiation, applied as a short-time treatment at room temperature, enhances the impact value of GFRPs at every fracture probability. The effect of EB-irradiation on the impact value of GFRPs mainly depends on the ductility enhancement of the GFRPs. EB-irradiation also enhances the reliability indicated by the minimum impact value (as), as well as the Weibull coefficient.
  • Microstructure and Mechanical Properties of Friction Stir Welded Dissimilar Aluminum Joints of AA2024-T3 and AA7075-T6

    pp. 1928-1937

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRA2007042

    Dissimilar aluminum alloys such as 2024-T3 and 7075-T6 plates 3 mm thickness were friction stir butt welded. The welding was carried out at a constant welding speed of 100 mm/min and rotation speeds of 400, 800, 1200, 1600 and 2000 min−1. Effects of rotation speeds and fixed location of two alloys on microstructures especially the homogeneity of elemental distribution in the stir zone (SZ), hardness distributions, and tensile properties of the joints were investigated. The homogeneity of constituents of the two alloys in the SZ was analyzed by a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDS).
    At the lowest rotation speed of 400 min−1 there was no mixing of two alloys in the SZ and a border between them was observed regardless of the fixed location. Increase of rotation speed more than 400 min−1 brought about a mixed structure likewise onion ring with periodic change of equiaxed grain size and heterogeneous distribution of alloying elements in the SZ. At 2000 min−1 of rotation speed the SZ mainly composed of the material fixed on the advancing side. The hardness increased in the zones occupied by 2024-T3 Al alloy and fluctuations took place in the SZ due to the onion ring at the higher rotation speeds till 1600 min−1. At 2000 min−1 of rotation speed the hardness of SZ mainly depend on the material fixed on the advancing side. Hardness minima was in the heat affected zone (HAZ) on the side of AA2024-T3 Al alloy and the values slightly increased as the rotation speed increased. In the case of transverse tensile test, defect-free joints were fractured at the HAZ on 2024-T3 side and a maximum tensile strength of the joints was achieved at 1200 min−1 of rotation speed when 2024-T3 Al alloy was located on the advancing side. On the other hand, the tensile properties of SZ in the longitudinal direction showed higher values when 7075 Al alloy was located on the advancing side.
  • Effect of Annealing on the Interfacial Structure of Aluminum-Copper Joints

    pp. 1938-1947

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MER2006371

    The aim of this study is to investigate the structure development and growth kinetics of the interfacial structure of cold roll bonded Al/Cu bimetal sheet. An interfacial structure is developed during the annealing process. The characteristics of the constituent phases at the interface of Al/Cu bimetal are studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results indicate that an obvious multi-layers interdiffusion structure is developed at the Al/Cu interface. The diffusion layer is consisted of four intermetallic compounds; Al2Cu, AlCu, Al3Cu4 and Al4Cu9. The growth of these intermetallics during annealing can be achieved by the diffusion process. The activation energies of Al2Cu, AlCu + Al3Cu4, Al4Cu9 and the total intermetallic layer are found to be 97.504, 107.46, 117.52 and 107.85 kJ/mol, respectively. These intermetallics generally possess higher hardness values than those of the corresponding base metals. AlCu and Al3Cu4 exhibit much higher hardness than that of Al2Cu and Al4Cu9, which implies lower fracture toughness. The observation of crack propagation paths shows that fracture mainly occurs in the intermetallic compound layers of AlCu and Al3Cu4, which are located between Al2Cu and Al4Cu9.
  • Interfacial Reaction in AZ91D Magnesium Alloy Matrix Composite Reinforced with Aluminum Borate Whisker

    pp. 1948-1954

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MER2007032

    AZ91D magnesium alloy reinforced with aluminum borate whisker (Al18B4O33w, denoted by ABOw) was fabricated by squeeze-casting. The heat treatment (T4) was carried out at 693 K in argon atmosphere for 48 and 96 hours, respectively, following water-quenched. The behaviors of interfacial reaction were studied in processes of fabrication and following heat treatment. Microstructures of interfacial reaction layers were investigated with transmission electron microscopy (TEM). Interfacial reaction layer in thickness of 5–10 nm was found in as-casted composite, and it was identified that the interfacial reaction layer was consisted of MgO. When the composite was heat-treated at 693 K for 48 hours, the surfaces of whiskers were covered with interfacial reaction layer completely and the thickness of interfacial reaction layer increased to about 20 nm. With increasing the time of heat treatment from 48 hours to 96 hours, the thickness of interfacial reaction layer on the surfaces of whiskers did not change obviously. The interfacial reaction layer was consisted of tiny MgO particles and a small quantity of MgB2 particles. Although MgO particles played a good barrier to keep out of contacting between magnesium and whisker, the boundaries between MgO particles acted as a shortcut of magnesium atoms migration. Therefore magnesium could keep on reacting to whisker. The interfacial reaction could invade into the inner of whisker about 20 nm depth after the composite was heat-treated at 673 K for 96 hours. The surfaces of whiskers became wave-like because of interfacial reaction. An orientation relationship was found between MgO reaction layer and ABOw: (11\\bar1)MgO||(320)ABOw and [011]MgO||[001]ABOw. The surfaces of MgO particles were consisted of close-packed (111)MgO plane.
  • Determination of Acid-Base Properties of Silicas by Inverse Gas Chromatography: Variation with Surface Treatment

    pp. 1955-1960

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MER2007076

    The specific component of the free energy of adsorption, −ΔGASP, of untreated crystalline and fused silica, and four types of silane coupling agents-treated fused silicas, were estimated by the inverse gas chromatography (IGC) method, using the adsorption of several polar and non-polar probes on their surfaces at various measuring temperatures. The acid-base properties of the untreated and surface-treated silicas were quantified by their KA and KD parameters, reflecting the ability of the surface to act as an electron acceptor and donor, respectively. Acidic components were detected on the untreated crystalline and fused silica surfaces, but the surface properties of the fused silicas surface-treated with γ-glycidoxy propyl trimethoxy silane (GMS) and γ-amino propyl triethoxy silane (AES) were slightly basic, and those of the fused silicas surface-treated with γ-methacryloxy propyl trimethoxy silane (MTMS) and γ-mercapto propyl trimethoxy silane (MCMS) were amphoteric.
  • Thermodynamic Properties of AlNd Determined by Low Temperature Heat Capacity Measurements

    pp. 1961-1964

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MER2007077

    The thermodynamic properties of AlNd were investigated by measuring the heat capacity, Cp, from near absolute zero (2 K) to 300 K using the relaxation method. During the measurement of the Cp(AlNd), 4 thermal anomalies were found on the Cp curve at 75.34, 39.79, 25.77, and 6.95 K. The third law entropy of AlNd at 298 K was obtained by integrating the polynomials for the measured Cp values. The result was as follows: S_298(AlNd)/J·K−1·mol−1=93.72±0.47. Using this value, the standard entropy of formation at 298 K was obtained as follows: Δ_fS^o_298(AlNd)/J·K−1·mol−1=-6.18±0.94.
  • Use of Laser Irradiation to Form Anti-Corrosive Surface Oxide Layer on Mg Metal

    pp. 1965-1968

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.L-MRP2007859

    Laser irradiation was used to improve the poor corrosion resistance of commercial grade pure magnesium (99.9 mass%) metal. The magnesium metal plates were immersed in a saturated Mg(OH)2 aqueous solution and the hydroxide layer formed on the plates was decomposed by laser-irradiation in air to form a uniform anti-corrosive oxide layer. Light scanning confocal microscopy (LSCM) was used to measure the thickness of the oxide layer and characterize the surface morphology of the laser-irradiated specimens. Corrosion resistance of the laser-irradiated specimens was evaluated by the method of hydrogen evolution during immersion using a 1 mass% NaCl aqueous solution. This study revealed that low speed-scanning with a low heat-input laser formed a thick, uniform MgO layer by decomposition of the Mg(OH)2 formed by primary immersion. The MgO layer prevented filiform corrosion and improved corrosion resistance of Mg metal.
  • Effect of Chloride Ion Concentration on the Fatigue Crack Growth Rate of a Zr55Al10Ni5Cu30 Bulk Metallic Glass

    pp. 1969-1972

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MRP2007085

    The effect of chloride ions on the fatigue crack growth rates of a Zr55Al10Ni5Cu30 bulk glassy alloy has been investigated by using a 3-point bending test method in NaCl solutions and phosphate buffered (PCA) solutions containing 0.1–0.5 kmol/m3 NaCl at room temperature. The crack growth rates increase with increasing chloride content, although the crack growth behavior in PCA + 0.1 kmol/m3 NaCl is almost the same as that in PCA without NaCl or in air. Another interesting feature is that the crack growth rates in the PCA + NaCl are lower than those in NaCl of the same content. The adsorbed phosphate ions at the crack tip of the specimen may prevent the adsorption of chloride ions, resulting in the decrease in the growth rates. SEM results reveal that the remarkably different fractography is obtained for the fatigue crack growth region in aqueous solutions containing the certain amount of chloride ions.
  • A New Method for the Production of Alloy Nanoparticles by Electrical Wire Explosion

    pp. 1973-1974

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MEP2007100

    The electrical wire explosion has been quite successful in the production of nanoparticles of various pure metals. However, the method failed to extend to the realm of alloys and intermetallics due in part to the unavailability of corresponding wires. In this paper, a new solution for this problem is suggested which utilizes electroplated wires instead. It is demonstrated that the explosion of Cu-plated Ni wire produce single phase CuNi alloy nanoparticles. The method is believed to have a potential to enable the synthesis of wide variety of alloy and intermetallic nanoparticles conveniently.

Article Access Ranking

18 Jan. (Last 30 Days)

  1. A Review of the Chemistry, Structure and Formation Conditions of Silico-Ferrite of Calcium and Aluminum (‘SFCA’) Phases ISIJ International Vol.58(2018), No.12
  2. Improving Blast Furnace Raceway Blockage Detection. Part 1: Classification of Blockage Events and Processing Framework ISIJ International Advance Publication
  3. Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling ISIJ International Vol.58(2018), No.12
  4. Hydrogen Embrittlement Susceptibility Evaluation of Tempered Martensitic Steels Showing Different Fracture Surface Morphologies Tetsu-to-Hagané Vol.105(2019), No.1
  5. Gasification and Migration of Phosphorus from High-phosphorus Iron Ore during Carbothermal Reduction ISIJ International Vol.58(2018), No.12
  6. Effect of Coke Size on Reducing Agent Ratio (RAR) in Blast Furnace ISIJ International Vol.58(2018), No.12
  7. Improvement of Sinter Productivity by Control of Magnetite Ore Segregation in Sintering Bed ISIJ International Vol.58(2018), No.12
  8. Heat Transfer Characteristic of Slit Nozzle Impingement on High-temperature Plate Surface ISIJ International Advance Publication
  9. High Temperature Thermal Diffusivity Measurement for FeO Scale by Electrical-Optical Hybrid Pulse-Heating Method ISIJ International Vol.58(2018), No.12
  10. Effect of TiO2 and MnO on Viscosity of Blast Furnace Slag and Thermodynamic Analysis ISIJ International Vol.58(2018), No.12

Search Phrase Ranking

18 Jan. (Last 30 Days)

  1. blast furnace
  2. blast furnace productivity
  3. blast furnace permeability
  4. 鉄と鋼
  5. laser welder
  6. titanium
  7. activity feo
  8. argon steel
  9. continous annealing
  10. eaf operation