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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 59 (2018), No. 6

  • Nanocluster Control for Achieving High Strength Aluminum Alloys

    pp. 861-869

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    DOI:10.2320/matertrans.M2017390

    High performance aluminum alloys with high strength, ductility and formability are strongly required and can be achieved through controlling precipitation microstructures, especially by utilizing nanoclusters, i.e. ‘nanocluster assisted microstructure control’. Nanoclusters are formed in the early stage of phase decomposition/precipitation and affect both the strength and subsequent precipitation, resulting in improved mechanical properties. Nanoclusters are small aggregates of solute atoms rapidly formed due to the strong attractive interaction among solute atoms and different from GP zones in composition and morphology. The formation kinetics and thermal stability of nanoclusters are affected by microalloying elements. The advanced 3-dimensional atom probe (3DAP) can detect nanoclusters and makes it possible to quantitatively determine their chemical composition, size and number density. In this article, the definition, formation behavior, influence on precipitation and mechanical properties of nanoclusters are presented based on our recent research on aluminum alloys. The combined addition of Mg and Ag to an Al–Cu alloy accelerates the nanocluster formation on the {111} planes of the matrix, resulting in a preferential formation of GP111 zones. In an Al–Zn–Mg alloy the addition of Ag increases the number density of finer GP zones and simultaneously decreases the width of precipitate free zones (PFZs). These are due to the strong attractive interaction of Ag with Mg and vacancies. On the other hand, the influence of nanoclusters on precipitation in Al–Mg–Si alloys is more complicated. It is emphasized that the well-known positive or negative effect of two-step aging basically originates from the Mg/(Mg + Si) ratio in the nanoclusters. Si-rich clusters cause the negative effect, while Mg–Si clusters cause the positive effect. The strength and ductility of aluminum alloys can be significantly improved by controlling nanoclusters. This Paper was Originally Published in Japanese in Materia Japan 56 (2017) 338–345. Figure 15 is modified with adding figures and Fig. 18 is newly added.
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    Readers Who Read This Article Also Read

    1. Effects of Scandium and Zirconium Addition on Recrystallization Behavior of Al–Mg–Si Alloy MATERIALS TRANSACTIONS Vol.59(2018), No.4
    2. First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron MATERIALS TRANSACTIONS Vol.59(2018), No.6
    3. Description of Thermal Vacancies in the CALPHAD Method MATERIALS TRANSACTIONS Vol.59(2018), No.4
  • First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron

    pp. 870-875

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    DOI:10.2320/matertrans.M2018014

    We report the effect of carbon on the phase transition between body centered cubic (BCC) and face centered cubic (FCC) in iron along Bain pathway, taking into account magnetic configurations, using density functional theory in combination with the generalized solid-state nudged elastic band method. We found that, for pure iron system, the energy barrier of 13.22 kJ·mol−1 is needed for the BCC-to-FCC process happens, while 2.41 kJ·mol−1 is needed for the reverse process (FCC-to-BCC). In the presence of carbon at the octahedral interstitial site of iron BCC/FCC lattice, the energy barrier of 4.53 kJ·mol−1 is needed for the transition from FCC to BCC while the 12.25 kJ·mol−1 is needed for a transition from BCC to FCC along the Bain path. Thus, carbon promotes the transition from BCC to FCC while it prevents the phase transition in opposite direction, from FCC to BCC. This is due to the local stress field formed in the vicinity of carbon atom which pushes the iron atoms aligning with carbon along [001] direction away.
  • Effect of Mineralogical Phase and Chemical Composition of Fly Ash on Electromagnetic Wave-Absorbing Properties

    pp. 876-882

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    DOI:10.2320/matertrans.M2017378

    In order to explore the electromagnetic radiation protection function of fly ash as building materials, Scanning Electron Microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Mössbauer were used to analyze the chemical composition and mineralogical phase of two types of fly ash. Electromagnetic parameters of the samples were analyzed and discussed in detail at the frequency range of 1∼18 GHz. The results showed that fly ash had electromagnetic wave absorbing property due to porous carbon grain and iron oxide, and that dielectric loss was more than magnetic loss for fly ash and electromagnetic property of type III was more than of type I. There were several absorbing-wave interference peaks at the frequency of 1–18 GHz, at thickness of 10–20 mm epoxy-based fly ash. The cement-based fly ash showed electromagnetic wave-absorbing properties at 10∼18 GHz and the biggest absorption reached 14.5 dB at 16 GHz at the thickness of 20 mm, so the fly ash should be expected to be a building material for electromagnetic protection.
  • Interaction Energies Among Rh Impurities in Pd and Solvus Temperatures of Pd-Rich PdRh Alloys

    pp. 883-889

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    DOI:10.2320/matertrans.M2017409

    We present the ab-initio calculations for the solvus temperatures (Tsolvus = 820∼860 K) of Pd1−cRhc (0.09 ≤ c ≤ 0.12) in which the Rh atoms are treated as impurities in Pd. The interaction energies (IEs) among the Rh impurities in Pd, being used in the real-space cluster expansion for the internal energies in the free energies, are determined by the ab-initio calculations based on the full-potential Korringa-Kohn-Rostoker Green’s function method, combined with the generalized gradient approximation in the density functional theory. The configurational entropy calculations are based on the cluster variation method within the tetrahedron approximation in which the 2∼4 body IEs are treated exactly within a tetrahedron of the 1st-nearest neighbor (nn) pairs. In order to take into account the 2-body IEs at the long-distance neighbors, we renormalize the 1st-nn 2-body IE by including the 2-body IEs up to the 10th-nn, because the 9th-nn 2-body IE is comparatively large. To realize the precise calculations for the Tsolvus of Pd1−cRhc, we also investigate the following three effects on the IEs among the Rh impurities: (1) the electron excitation due to the Fermi-Dirac distribution, (2) the thermal lattice vibration by the Debye-Grüneisen model, and (3) the local lattice distortion for the 1st-nn 2-body IE. The calculated results for the Tsolvus of Pd1−cRhc agree fairy well (within the error of ∼50 K) with the observed Tsolvus.
  • Thermodynamic Stability of Mg-Based Laves Phases

    pp. 890-896

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    DOI:10.2320/matertrans.M2018079

    To investigate the stability of various Mg-based Laves phases, the formation enthalpy and phonon dispersion were obtained by first-principles calculation. The calculated formation enthalpy and phonon dispersion indicate that MgX2 (X = Al, Co, Ni, Cu, Zn) and Mg2X (X = Ca, Sr, Y, Ba, La) are stable both statically and dynamically. These results are consistent with the experimental results except for MgAl2 and Mg2La. These compounds are considered to be in a metastable state in each binary system. We also used the cluster expansion method to examine the possibility of adding a third element to MgZn2. Our theoretical investigations suggest attractive interaction between Zn and a third element such as Ag, Ca, and Zr in the MgZn2 lattice. However, Ca and Zr replace a small amount of Zn in MgZn2 owing to the instability of MgCa2 and MgZr2, in agreement with the experimental result. Furthermore, it is suggested that Zr becomes stable at the Mg site in the MgZn2 lattice owing to the stability of ZrZn2.
  • Effect of Additive Elements on the Elinvar and Invar Characteristics of Fe–Mn Base Alloys

    pp. 897-902

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    DOI:10.2320/matertrans.MBW201709

    This study investigated the temperature dependence of the Young’s modulus and the thermal expansion of Fe–26 at%Mn base alloys. The addition of a few % of Ti, Mo, Nb, Zr, Ta, or Hf to the alloys limited the temperature coefficient of Young’s modulus to within ±5 × 10−5/K. In alloys with added Nb, Zr, and Hf, the temperature coefficient of thermal expansion was 1 × 10−5/K or less, whereas the Néel temperature was 380 K or greater. Fe–Mn-based alloys containing a few at% of elements from families 4 and 5 of the periodic table exhibited both Elinvar and Inver characteristics at temperatures up to approximately 380 K. The effect on the properties was shown to be correlated with the number of electrons in the outer shell of the added element and its atomic radius.
  • In-Situ Study of Phase Transformation and Microstructural Evolution of Ni45Mn37In13Co5 Metamagnetic Shape Memory Alloy

    pp. 903-907

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    DOI:10.2320/matertrans.M2017415

    This paper aims to study the phase transformation and microstructural evolution of Ni45Mn37In13Co5 metamagnetic shape memory alloy during heating and cooling in terms of differential thermal analysis, thermo-magnetic analysis, and temperature-variable optical Kerr microscopy. It has been found that two-stage phase transformation occurs for the alloy during heating. The first stage is magneto-structural transition from low-magnetic martensite to ferromagnetic austenite with a transformation entropy change of about 30.5 J kg−1 K−1, and the other is pure magnetic transition from ferromagnetic austenite to paramagnetic austenite. In-situ observation of microstructural evolution at one given position during heating shows that the austenite transformation begins at 359 K (inferred as As), reaches a peak value at about 6 K above the As and ends at 375 K. Meanwhile, the temperature when the lath-like martensite begins to disappear (or appear) differs at different region, suggesting that various degrees of superheat (or supercool) and nucleation energy barriers are needed for different martensitic variants. However, one common feature in transformation at these different regions is that the collective formation of a series of austenite (martensite) plays a dominant role.
  • Hot-Cracking Mechanism in Al–Sn Alloys from a Viewpoint of Measured Residual Stress Distributions

    pp. 908-916

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    DOI:10.2320/matertrans.M2018011

    A study was carried out with Al–Sn alloys having eutectic system aiming at understanding the hot-cracking mechanism considering the factors of temperature, stress and element distribution in the vicinity of cracks. According to the temperature measurement in the cast Al–30 mass%Sn alloy, cracking was initiated at 820 K (547°C) which corresponded to 0.9 in solid fraction. It was observed that the crack was initiated at the position close to the center but a little bit mold side and propagated toward the Cu and refractory sides. The crack became longer with an increase in Sn content. According to the residual stress distribution, almost zero stress remained in the Sn phase along the hot-crack indicated that the crack was attributed to the liquid film of the Sn phase. On the other hand, compressive stress remained in the both Al and Sn phases beyond the crack-tip indicating ductile behavior in this region. Observation of the fracture surfaces showed that the Sn phases exhibited globular shapes indicating that Sn melted consistently with the results of stress measurement showing almost zero stress values. Therefore, hot-cracking mechanism was clarified as a fracture firstly took place at 0.9 in solid fraction due to the liquid film of Sn. After that, ductile fracture occurred at the positions almost solidified when the crack was initiated.
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    Readers Who Read This Article Also Read

    1. First-Principles Study of BCC/FCC Phase Transition Promoted by Interstitial Carbon in Iron MATERIALS TRANSACTIONS Vol.59(2018), No.6
    2. Nanocluster Control for Achieving High Strength Aluminum Alloys MATERIALS TRANSACTIONS Vol.59(2018), No.6
  • Influence of Thermal Ageing and Specimen Size on Fracture Toughness of Z3CN20-09M Casting Duplex Stainless Steels

    pp. 917-921

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    DOI:10.2320/matertrans.M2017345

    To assess the thermal aging embrittleness of the primary coolant pipes in pressurized water reactor (PWR), the fracture toughness test is conducted for Z3CN20-09M CDSSs thermally aged at 400°C for 10,000 h and the fracture morphologies of the virgin and the aged specimen are analyzed based on SEM technique. The influence of the specimen thickness and thermal ageing time on the fracture toughness of the material is discussed in details. The results show that with increasing thermal ageing time, the JIC of Z3CN20-09M CDSSs significantly decreases and the fracture mechanism transits from the ductile microvoid coalescence fracture to the cleavage fracture in ferrite and the quasi-cleavage fracture in austenite. Moreover, the theoretical expression between the fracture toughness KC and the specimen thickness t of Z3CN20-09M CDSSs is established, which can be used to estimate the fracture toughness with different specimen thickness.
  • The Effect of Aluminum Dihydrogen Phosphate on the Enhanced Mechanical Properties of Aluminum Foams

    pp. 922-926

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    DOI:10.2320/matertrans.M2017247

    Powder metallurgy route was employed to fabricate aluminum (Al) foams with open and small cells. Starch acetate powder was adopted as a space holder, which evaporates during carbonization and leaves behind pores in the Al matrix. Aluminum dihydrogen phosphate (ADP) was used as binding agent between Al particles in present work. Cell diameters of Al foams range from several microns to thousands of microns, and cell geometry depends mainly on the distribution of starch acetate particles during mixing process. The phase compositions were characterized by X-ray diffraction (XRD). The scanning electron microscopy (SEM) together with energy dispersive X-ray spectroscopy (EDS) suggests the existence of carbon produced along cell wall after annealing. Subsequently, a uniaxial compression test was performed to study the effect of ADP content on mechanical properties and absorption abilities of Al foams. It is shown that both mechanical property and energy absorption ability are improved with appropriate amount of ADP.
  • Hyperbaric-Oxygen Accelerated Corrosion Test for Iron in Cement Paste and Mortar

    pp. 927-934

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    DOI:10.2320/matertrans.M2018029

    A novel accelerated corrosion test method which enhances oxygen supply has been proposed for reinforcing steel in concrete in this study. Oxygen reduction current density (ORCD) was measured by means of potentiodynamic polarization test for an iron specimen embedded in cement paste or mortar in a saturated Ca(OH)2 solution in ambient air. The ORCD decreased with an increase in cover thickness and the current density was reciprocally proportional to the cover thickness from 1 mm to 10 mm, suggesting that diffusion limited oxygen reduction can be accelerated by reducing the cover thickness below 10 mm. The oxygen supply to iron surface in cement paste or mortar was enhanced by pressurized oxygen gas using a newly developed hyperbaric-oxygen accelerated corrosion test container. Iron specimens with 5 mm cement paste and mortar covers showed almost 25 times higher ORCD in 0.5 MPa oxygen gas than that in ambient air, respectively. The iron specimens covered with 5 mm of cement paste or mortar containing chloride ion were immersed in a saline solution and exposed to 0.5 MPa oxygen gas in the container for 30 days. The thickness of the rust layer formed for 30-days was in good agreement with that estimated from the ORCD obtained in 0.5 MPa oxygen gas, indicating that the corrosion was accelerated in proportion to the oxygen (partial) pressure. Furthermore, the rust formed in pressurized oxygen gas showed similar characteristics to that formed in a practical service environment. Thus, the hyperbaric-oxygen is beneficial and effective to validly accelerate the corrosion of reinforcing steel in concrete. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 82 (2018) 1–7. The sample name described in Table 2 was changed.
  • Fabrication of Defect-Free Fe–Mn Alloys by Using Electrodeposition

    pp. 935-938

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    DOI:10.2320/matertrans.M2018010

    Nanocrystalline Fe–Mn alloys for molds with high strength, high thermal stability, and relatively low cost were prepared by electrodeposition. We used electrolytes that primarily consisted of iron sulfate and manganese sulfate combined with manganese chloride. Since electrodeposited Fe–Mn alloys tend to include many defects that greatly reduce their mechanical properties, we developed a method for reducing the number of defects in Fe–Mn alloys. The presence of surface cracks was strongly related to the orientation index for the (200) plane, which can be controlled by the amount of Mn. The number of voids was decreased as the current efficiency increased by controlling the current density and pH. An Fe–Mn alloy with no surface cracks was successfully fabricated by optimizing the current density and Mn/Fe molar ratio.
  • Strontium Doping Effect on High-Temperature Oxidation of Nano-Ni Dispersed Alumina Composites

    pp. 939-943

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    DOI:10.2320/matertrans.M2017391

    Two sets of 0.1 mol% Sr-doped 5 vol% Ni/Al2O3 and undoped 5 vol% Ni/Al2O3 samples were fabricated by the pulsed electric current sintering technique to investigate the influence of Sr-doping effects on the high-temperature oxidation. Oxidation tests were conducted in air at temperature ranges of 1200–1400°C for 1–10 d. Oxidation of Ni within the matrix at high temperatures induced formations of the top surface layer and the oxidized zone. The top surface layer was composed of the oxidation product-NiAl2O4, while the oxidized zone consisted of Al2O3 matrix and NiAl2O4. Formation of the oxidized zone of undoped and Sr-doped samples followed the parabolic law. The parabolic rate constant of Sr-doped samples was approximately two times smaller than that of undoped samples. The apparent activation energies on the growth of the oxidized zone were determined to be 479 and 476 kJ/mol for undoped and Sr-doped 5Ni/Al2O3, respectively. Sr-doping reduced oxygen transport along Al2O3 grain boundaries and enhanced the high-temperature oxidation resistance of Ni/Al2O3.
  • Electrodeposition of Aluminum–Tungsten Alloy Films Using EMIC–AlCl3–W6Cl12 Ionic Liquids of Different Compositions

    pp. 944-949

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    DOI:10.2320/matertrans.M2018051

    Electrodeposition of Al–W alloy films with high W contents has been carried out using 1-ethyl-3-methylimidazolium chloride (EMIC)–aluminum chloride (AlCl3) ionic liquids containing tungsten(II) chloride (W6Cl12). Although the corrosion resistance and hardness of the alloy films are expected to be improved with an increase in the W content, dense films with W contents higher than ∼12 at% have not been obtained by electrodeposition to date. This study has demonstrated that electrodeposition using a EMIC–AlCl3–W6Cl12 bath with a lower AlCl3/EMIC molar ratio can yield Al–W alloys with higher W contents. The maximum W content of the alloys electrodeposited using the EMIC–1.5AlCl3 bath reached 19.4 at%. The alloy films with up to ∼18 at% W were dense and smooth, whereas those with >∼18 at% W exhibited increased surface roughness. The hardness and Young’s modulus of the dense and smooth 17.7 at% W film were determined by nano-indentation. The hardness of this film was confirmed to be higher than those of the Al–W alloy films previously obtained from the EMIC–2AlCl3 baths.
  • Influence of Thermal Boundary Conditions on the Results of Heat Treatment Simulation

    pp. 950-956

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    DOI:10.2320/matertrans.H-M2018816

    Surface hardening heat treatment, including carburizing and quenching, is widely used to prevent wear and rolling contact fatigue of vehicle power transmission system parts such as gears. However, distortion that occurs during heat treatment processes can present problems for improving the precision of gear shapes. Predicting distortion behavior accurately by a heat treatment simulation method could help to achieve better heat treatment quality and accuracy of parts. A heat treatment simulation of a gear tooth was carried out in this work by using the heat transfer coefficient during a gear heat treatment process. The tooth surface was divided into nine parts with different heat transfer coefficients. It was found that the difference between the actual deformation and the calculated deformation was smaller compared with the application of a uniform heat transfer coefficient at the tooth surface. By considering the distribution of heat transfer coefficient on the tooth surface for width and height direction, the heat treatment deformation prediction result became more accurate.
  • Dynamic Measurement of Constraining Force from Green Sand and Casting Contraction of Gray Cast Iron during Cooling

    pp. 957-962

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    DOI:10.2320/matertrans.F-M2018817

    This study investigated the effects of the restraint from green sand mold for cast iron during cooling process. Gray cast iron (JIS FC300, almost identical to ASTM 45) was cast in a green sand mold, and the constraining force to the casting from the sand mold and the contraction of the casting were measured dynamically from the beginning of solidification to 200°C. The measurement results obtained using the green sand mold were compared with those using the furan sand mold. The maximum constraining force in the green sand mold case was lower than that in the furan mold case. The contraction in the green sand mold at 200°C was greater than that in the furan sand mold. The results showed that the green sand mold restrains the casting less than the furan sand mold during cooling process.
  • Thermally Stable Conditions during Capillary Shaping of Bent Components

    pp. 963-968

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    DOI:10.2320/matertrans.F-M2018818

    Capillary shaping is an upward pulling solidification technique for obtaining aluminum alloy hollow products with high structural stiffness and high mechanical properties. Recently, hollow frames with inner ribs and bent geometry are increasingly desired for optimizing car body stiffness and design of lightweight car body structures. Capillary shaping is an attractive process for manufacturing these components. However, it is necessary to control thermal conditions during the pulling process for fabricating bent products with high thickness accuracy, since thermal conditions influence the thickness of products and vary at the bent section due to differences in the pulling rates at inner and outer positions. In this study, the thermally stable conditions during the capillary shaping of aluminum alloy bent tubes were investigated. It is found that bent tubes with high thickness accuracy can be fabricated without any automatic controls of cooling conditions when thermally stable pulling conditions are maintained. This Paper was Originally Published in Japanese in J. JFS 89 (2017) 396–401.
  • Brazed Bonding between SiAlON and Heat-Resistant Alloys with Application of Filler Materials

    pp. 969-975

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    DOI:10.2320/matertrans.M2018038

    It has been required to improve the heat efficiency of thermal power generation system for the sake of mitigation of the global warming and resource depletion problems. For improving the heat efficiency, it is effective to increase the steam temperature, and as a result, appropriate heat-resistant alloys are needed. Although SUS304 stainless steel and Ni-based superalloys have been proposed as promising heat-resistant alloys until now, there still remain some concerns such as high-temperature corrosion by flaming gas and erosion by combustion ash. Thus, the present authors propose SiAlON ceramic coating on SUS304 and INCONEL X-750 because SiAlON has excellent heat, wear and corrosion resistances. In the present study, brazed bonding between SiAlON and these heat-resistant alloys was attempted with the applications of Cu and Ag as a soft filler material to reduce the residual stress generated due to the difference in thermal expansion coefficient between SiAlON and the heat-resistant alloys. As for the bonding with the Cu filler, the SiAlON/Cu/SUS joint was successful when the brazing time was short. However, when the brazing time was long (for example, 60 minutes), Fe-based grains were formed in the Cu filler layer, and the cracks were formed in the SiAlON near the joint interface during cooling in the brazing process. It was considered that the Cu filler was hardened by the formation of the Fe-based grains and could not reduce the residual stress. As for the bonding with the Ag filler, on the other hand, the SiAlON/Ag/SUS joint was successful even for a long brazing time. The SiAlON/Ag/INCONEL joint was also successful. The bending strengths of these SiAlON/Cu/SUS, SiAlON/Ag/SUS and SiAlON/Ag/INCONEL joints were evaluated by a three point bending test, and the results were approximately 200, 270 and 350 MPa, respectively. In all cases fracture occurred in the SiAlON, which means that the SiAlON and the alloys were strongly bonded. This Paper was Originally Published in Japanese in J. Japan Inst Met. Mater. 81 (2017) 143–149.
  • Quantification of Localized Water Image in Under-Film Corroded Steel with High Spatial Resolution, High Time Resolution, and Wide View by Neutron Radiography

    pp. 976-983

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    DOI:10.2320/matertrans.M2018017

    Information on the existence of localized water at corrosion locations is indispensable for precisely understanding the corrosion mechanism in steel. Small amounts of localized water in under-film corrosion have not yet been measured quantitatively.Although we have demonstrated that neutron radiography, which has high sensitivity to the presence of hydrogen, is suitable method for detecting of water in the under-film corrosion of painted steel by utilizing the RIKEN Accelerator-driven Neutron Source (RANS), the spatial and time resolutions were insufficient to investigate under-film corrosion in detail. We then performed an imaging experiment on localized water in steel corrosion with higher space and time resolutions using the high-intensity neutron source at J-PARC. We obtained data with a spatial resolution of 0.6 mm, a time resolution of 15 s in a viewing area of 100 × 100 mm2. On the basis of the results for the quantitative imaging of localized water in corrosion, we have established a method suitable for directly imaging water in steel corrosion that employs neutrons.
  • Pyrometallurgical Separation of Indium Phosphide through the Phosphorous Removal by Iron and the Chlorination Process Utilizing Ammonium Chloride

    pp. 984-988

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    DOI:10.2320/matertrans.M2018007

    Pyrometallurgical chlorination process has been employed for the recovery of elements from indium phosphide, InP, one of the important III–V semiconductor materials. It was found that both indium and phosphorous were converted to volatile species, indium chloride and phosphine, PH3, by thermal treatment of InP powder in the presence of ammonium chloride. However, the recovery as volatile compounds reached ∼60% at reaction temperature of 800°C. Based on these results we have employed the thermal treatment of the mixture of InP and iron powders. Phosphorous could be successfully converted to non-toxic iron phosphide, Fe3P. The consequent chlorination reaction resulted in the indium recovery of ∼100% in volatile form. The influence of reaction conditions, such as reaction temperature and composition of ammonium chloride, was examined.
  • Dynamic Material Flow Analysis and Forecast of Copper in Global-Scale: Considering the Difference of Recovery Potential between Copper and Copper Alloy

    pp. 989-998

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    DOI:10.2320/matertrans.M2017399

    The recovery of copper (Cu) from secondary sources has received much attention because of its scarcity of natural resources. In this work, we estimated the input, in-use stock and discard of copper and copper alloy during 1950–2015 in global scale, and forecast them until 2050. In addition, we estimated the potential of scrap recovery for copper/copper alloys. It was estimated that the total amount of in-use stock of copper and copper alloy were 177,000 kt and 44,200 kt in 2015, respectively. The in-use stock, discard and input of copper in 2050 will reach 381,000–588,000 kt, 15,400–22,200 kt and 18,990–33,000 kt, respectively, whereas those for copper alloy will reach 77,500–134,000 kt, 3,020–4,680 kt and 3,760–7,200 kt, respectively. The copper content in recoverable scraps of copper and copper alloy will reach 15,100–27,300 kt, and this accounts for 55.1–79.0% of copper content in annual input of copper and copper alloy in 2050. The range in forecast was caused by the difference in the saturation amount of in-use stock per capita and recovering rates of scraps. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 82 (2018) 8–17. Reference 38) was added in order to more precisely explain.
  • Fabrication of Aluminum Foam Core Sandwich Using Sandwich-Type Foamable Precursor with Two Face Sheets by Friction Stir Welding Route

    pp. 999-1004

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    DOI:10.2320/matertrans.M2018037

    An aluminum foam sandwich (AFS), which consists of an aluminum (Al) foam core and two dense metallic face sheets, is a lightweight component material with good energy and sound insulation properties. A fabrication method for AFSs that can simultaneously fabricate a foamable precursor and realize metallurgical bonding between the precursor and a dense metallic sheet was proposed using the friction stir welding (FSW) route. In this study, we produced a sandwich-type foamable precursor with two Al face sheets using the FSW route and, by foaming this precursor, an AFS was fabricated. Through X-ray computed tomography inspection of the AFS and observation by an electron probe microanalyzer, it was confirmed that no cracklike pores existed in the Al foam core and that only few pores generated by the foaming entered the Al face sheet. Moreover, static tensile tests of the AFS were carried out, and it was shown that the tensile strength of the Al foam core was not decreased by the existence of an oxide film and that the bonding strength of the interface between the Al foam core and the Al face sheet was higher than the tensile strength of the Al foam core.
  • Synthesis and Thermal Stability of B20-Type TMGe (TM = Mn, Fe and Co) Intermetallic Compounds Prepared by Mechanical Milling

    pp. 1005-1008

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    DOI:10.2320/matertrans.M2018016

    We propose a new synthesis method of transition-metal monogermanides (TMGe, TM = Mn, Fe, and Co) with a B20-type chiral structure. Arc-melting followed by mechanical milling can be used to produce ∼70–110 Å-sized B20-type structures. Differential scanning calorimetry and heat-treatment tests indicated that the B20-phases are stable below 673 K, 873 K and 773 K for MnGe, FeGe and CoGe, respectively. We also demonstrated that sintering tests are able to yield dense compacts from the FeGe and CoGe B20-phase powders.
  • Combination of High-Pressure Torsion with Incremental Feeding for Upsizing Sample

    pp. 1009-1012

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    DOI:10.2320/matertrans.M2018039

    This study introduces an advanced process solving the limitation involved in the process of high-pressure torsion (HPT). The HPT process is now well recognized as an effective process for significant grain refinement through severe plastic deformation (SPD) in many metallic materials including hard-to-deform materials. However, the applicability of the HPT process is limited to rather small diameters of disks or rings. The new proposed process, which we call incremental feeding HPT (IF-HPT), incorporates consecutive incremental feeding in the conventional HPT process to increase the SPD-processed area. The IF-HPT process is developed based on the principle of our recent SPD process called the incremental feeding high-pressure sliding (IF-HPS). The IF-HPT is applied to a Ni-based superalloy, Inconel 718, and it is demonstrated that the high-strain rate superplasticity is achieved with elongation well more than 400% at 1073 K and an initial strain rate of 2 × 10−2 s−1. It is also proposed that the IF-HPT process can be used to increase the SPD-processed area by lateral feeding of the sheet sample as the IF-HPS developed earlier.

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