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. 52 (2011), No. 3

  • Superconducting Properties of MgB2 Particle Impregnated with Mg-Based Alloys

    pp. 272-275

    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.MB201002

    The three-dimensional penetration method combined with semi-solid casting (SS-3DPC) was utilized to prepare magnesium diboride (MgB2) powder composite materials with various host materials of Mg, Mg-3%Al, Mg-3%Al-1%Zn, Mg-9%Al, and Mg-9%Al-1%Zn. X-ray diffraction measurements indicated predominant peak patterns of MgB2 and a host alloy, implying that the host material tightly bonded MgB2 grains without melting the MgB2 powder. This was confirmed by SEM images. Measured electrical resistivity and magnetization versus temperature showed clear signals of superconducting transition temperature of 27∼38 K for all the samples cut out from the billets. Magnetic hysteresis loop observed at 5 K enabled us to estimate a critical current density (Jc) based on the extended Bean model. Additions of aluminum and zinc elements to magnesium host-matrix were found to enhance Jc and increase residual resistivity (ρ0) suggesting that aluminum and zinc have an effect on pinning magnetic flux flow for Jc enhancement, and scattering conduction electrons for increase of ρ0.
  • EELS and Ab-Initio Study of Faceted CSL Boundary in Silicon

    pp. 276-279

    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.MB201018

    Faceted Σ3 CSL grain boundaries in silicon were investigated by high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS) and ab-initio calculation. A {112} Σ3 CSL boundary consisted of two segments which differed in atomic structure. The segment near the connected corner to {111} Σ3 CSL boundary showed symmetric structure and the other long segment, being distant region from the corner, showed asymmetric structure. In the symmetric segment a 5-fold coordinated atom presented, which produced a deep state in the band gap. A pronounced shoulder, which could be attributed to the defect state above Fermi level, was detected only in Si-L23 energy-loss near-edge spectra (ELNES) acquired from the symmetric segment of the {112} Σ3 CSL boundary near the CSL junction.
  • Interface Structure of Gold Particles on TiO2 Anatase

    pp. 280-284

    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.MB201004

    Gold particles supported on titanium dioxide (TiO2) are known to activate many catalytic reactions. In this study, interface structure of gold on anatase was examined in the case on an anatase {101} surface, since the surface is the most important for several photocatalytic reactions. Anatase TiO2 nanorods having clear washboard-like {101} outer surfaces were synthesized by using a double surfactants system. From high resolution electron microscopy observation for gold particle on the {101} surface, the (113) plane of gold was found to be parallel to the (101) surface of TiO2. Such an epitaxy is corresponding to be the axial and planar orientations of [03\\bar1] (200)Au || [\\bar31\\bar1] (113)TiO2, being originated from the smallest lattice mismatching, instead of the previous cases of [01\\bar1] (111)Au || [02\\bar1] (112)TiO2 on the {110} and {112} surfaces of anatase TiO2.
  • Grain Boundary and Intragranular Reactions during Aging in Mg-Al System Alloys Poured into Sand and Iron Molds

    pp. 285-291

    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.MB201011

    It is well-known that age hardening occurs in Mg-Al system alloys, when the alloy containing aluminum exceeds 6 mass%. This precipitation reaction depends on the aluminum content and aging temperature. The aging behavior in AZ91 magnesium alloy was investigated and it is the subject of this paper. However, for the Mg-Al system alloys, the influence of aluminum content on age hardening characteristics has not been researched in detail so far. In this study, continuous and discontinuous precipitations during aging in Mg-Al system alloys cast into sand and iron molds was investigated by means of hardness measurement and microstructure observation with optical microscope and transmission electron microscope. The microstructure of AM60 magnesium alloy with 6 mass% containing aluminum in the as cast condition was composed with a primary crystallized alpha magnesium phase and beta Mg17Al12 phase. The hardness of cellular precipitates existing near the grain boundary in sand mold castings decreased with increasing the aging time. On the other hand, the hardness of intragranular precipitates was constant against the aging time. Variation of hardness with aging was found to be caused mainly by the discontinuous precipitation along the grain boundaries from the composite rule in hardness. In iron mold castings, it was found that the variation of hardness with aging was found to be caused mainly by the continuous precipitation inside the crystal grain.
  • FIB Induced Damage Examined with the Low Energy SEM

    pp. 292-296

    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.MB201005

    The surface morphology of pure Mg was studied by means of the cathode lens mode equipped scanning low energy electron microscope after bombarding with Ga+ ions at various energies (10, 20, 30, and 40 keV) and incident angles (0°, 30°, 45°, and 60°). In accordance with the Bradley-Harper theory at off-normal angles of incidence ripples were observed on the irradiated areas. The Monte Carlo program SRIM2008 was used to estimate the sputtering yield and damage depth.
  • Fine Structure of Wing Scales in Chrysozephyrus Ataxus Butterflies

    pp. 297-303

    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.MB201001

    We performed scanning electron microscopy observations of the scales on the dorsal surfaces of wings of male and female Chrysozephyrus ataxus butterflies. The male butterfly has curly scales on the blue or green wings. It was deduced that the interference of the selective incident rays with the wavelength λ in ∼560nm≥λ≥∼420nm and ∼340nm≥λ≥∼250nm occurs incoherently by layers ∼270 nm thick piled in the flat grooves which are enclosed by the ridges and ribs on the curled scale. The metallically glittering green-violet hues of the male wings is thereby attributed to the reflection of the human visible rays in ∼560 nm (green) ≥ λ ≥ ∼420 nm (violet). The vivid violet marks in the female’s forewings were also explained as the result of reflection of the incident rays in ∼400nm≥λ≥∼300nm from the layers ∼190 nm thick in the flat grooves on the dorsal scale. Although the monolayered cuticle structure was observed on the ridges of these scales, its contribution to the wing colouration must be less because of a small width of the ridges as compared with the flat grooves. The scales in the dark brown areas of the female wings are different in structure from these scales; they have not any layers but windows enclosed by the ridges and ribs. Most of the light through the windows is absorbed in the lower laminae containing the eumelanin. These results were deduced using data of a previous optical measurement by Imafuku et al. (Zool. Sci. 19 (2002) 175) and elucidated consistently their conclusion.
  • Aluminum Alloy Based Nanocomposites Strengthened with Amorphous AlNiTiZr Phase

    pp. 304-308

    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.MB201006

    The concept to design a composite of the 7475 alloy strengthened with particles of an amorphous aluminum based alloy was studied in the present paper. Mechanical alloying (MA) process was applied to obtain amorphous structure of the powder of composition Al70Ni10Zr10Ti10 (in at%). Elemental powders of this composition were ball milled for 60 h in a planetary high energy mill using steel balls. The estimated mean size of powder particles below 10 μm was much smaller than that of the initial elemental powders. The mean value of the microhardness of the milled powder was 384 HV and was significantly higher than that of initial powders. The dominant presence of the amorphous structure was confirmed using DSC studies, in which crystallization peaks were observed above 400°C. X-ray diffraction (XRD) patterns after various milling times confirmed a partial amorphization of the material. Additionally, weak maxima of Al3Zr4 phase were identified. TEM studies of powders confirmed the formation of predominantly amorphous structure with some nanocrystalline inclusions of intermetallic phases identified as Al3Zr4, AlZr3, Al3Ni and Al3Ti. The amorphous powder was mixed (for a short time) with prealloyed 7475 alloy powder 40 h ball milled to obtain nanocrystalline grain size of powder’s particles. Powders were hot pressed in vacuum, below the crystallization temperature at 380°C and pressure of 600 MPa in order to preserve amorphous and nanocrystalline grain structure. SEM studies of the composite containing 1/3 ball milled 7475 alloy and 2/3 of the amorphous powder allowed identifying low porosity and clean interface within the composite. The samples showed compression strength near 500 MPa and a few percent ductility. The cracks nucleated within the amorphous particles as resulted from SEM studies of the compressed samples.
  • Microstructure of Rapidly Solidified Al-12Zn-3Mg-1.5Cu Alloy with Zr and Sc Additions

    pp. 309-314

    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.MB201009

    The rapid solidification of Al-12 Zn-3 Mg-1.5 Cu (in mass%) alloy was investigated in order to determine structure changes and the effect of Zr or Sc+Zr additions. Rapidly solidified ribbons with the thickness of 30–50 μm were obtained by a melt spinning technique. The alloys cast into a copper mould were used as a reference material. The mould cast alloys as well as the melt spun ribbons revealed the dendritic microstructure of α(Al) solid solution and η (MgZn2) phase in the interdendritic areas. Additionally the T-Mg32(Zn, Al)49 phase with icosahedral quasicrystalline symmetry was found in the form of small particles located mainly at the wheel side in the Zr or Zr+Sc containing ribbons. The refinement of the microstructure and the reduction of volume fraction of the η phase was observed in the ribbons. Large Al3Zr primary precipitates were observed in the mould cast alloy containing zirconium, while almost whole Zr in the ribbons dissolved in the aluminium solid solution. Annealing of ribbons at 400°C led to the precipitation of spherical L12-Al3Zr or Al3(Sc, Zr) particles, coherent with the matrix. They could be responsible for the improvement of properties of the aluminium alloys by the retardation of recrystallization and grain growth. Plate like precipitates of metastable η′ phase appeared after ageing at 120°C and led to the increase of microhardness up to about 230 HV.
  • TEM Characterisation of Silicide Phase Formation in Ni-Based Ohmic Contacts to 4H n-SiC

    pp. 315-318

    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.MB201014

    Nickel silicide ohmic contacts to 4H n-SiC were investigated using electron microscopy. Ni/Si multilayer structures were fabricated using magnetron sputtering technique. The Ni to Si layer thickness ratio was chosen to achieve the stoichiometry of Ni2Si phase. The deposited structure was subjected to a two-step annealing procedure. First annealing step was performed at 600°C, the second at 1050°C or 1100°C. Microstructure and morphology after each annealing step were characterized using scanning and transmission electron microscopy. The specific voids and discontinuities of the layer were observed after annealing at high temperature. Phase compositions were investigated with electron diffraction technique. After annealing at 600°C the phases Ni2Si, Ni3Si2 and Ni31Si12 were detected. High temperature annealing resulted in the presence of only Ni2Si phase. The influence of phase transformations on the morphology of the contacts is discussed. Explanation of the origin of layer discontinuities is proposed.
  • Phase Characterization of Re-Based Diffusion Barrier Layer on Nb Substrate

    pp. 319-323

    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.MB201022

    An electron microscopy phase characterization was carried out for a Re-based diffusion barrier layer, which was deposited on the Nb substrate used as an ultra high temperature material. The coating process produced three layers; an outer Cr(Re) layer, an intermediate Cr-Nb-Re layer, and an inner Nb(Re) layer. The Cr-Nb-Re layer is considered to act as a diffusion barrier layer between the substrate and the outer Cr(Re) reservoir layer. The Cr(Re) and Nb(Re) layers are in single phase with a similar bcc structures, but they are different in structure from the intermediate layer, which is composed of a dual phase of Re63Cr20Nb17 with a cubic structure and Nb42Re33Cr25 with a hexagonal structure determined by transmission electron microscopy (TEM) in this study.
  • Nucleation Behaviour of β to ω Phase Transformations in β-Type Ti-Mo Alloys

    pp. 324-330

    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.MB201017

    Nucleation behaviour of β to ω phase transformations in β-type Ti alloys has been investigated using electron microscopy in four cases; (1) along the {112}⟨11\\bar1⟩ twin boundary, at which compressive stress occurs, (2) by means of aging under tensile stressing, (3) on the effects on the amounts of quenched-in vacancy in specimens quenched-in from two different temperatures, and (4) due to cooling to 131 K. Results show that the formation of nucleation-sites is enhanced by both compressive-stress along the twin boundary and tensile-stress during aging. In a specimen quenched from a higher temperature, the formation of nucleation-sites increases. It is considered that quenched-in vacancies and their clusters become nucleation-sites of β to ω phase transformations. The phase transformation occurs due to cooling to 131 K. It is also found that the formation of new nucleation-sites cannot be reproduced and that they moved randomly.
  • Particle Size and Morphology of Iridium Oxide Nanocrystals in Non-Volatile Memory Device

    pp. 331-335

    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.MB201020

    The aim of this work is to investigate the particle size and morphology of the nanocrystals in the non-volatile memory device by annular dark field (ADF) scanning transmission electron microscopy (STEM) and conventional transmission electron microscopy (CTEM) techniques. With respect to TEM investigation, statistical analysis on STEM image can acquire the size and density of nanocrystals more accurately than on TEM image. In addition, ADF STEM images successfully provide powerful evidences revealing the structure of IrOx nanocrystals as a core shell structure, where the inner structure is rich in Ir and the outer area is abundant in O or Al. This method could be one of the efficient way for examining the nanocrystals with a complicated cored structure.
  • Microstructure Stability of 4th Generation Single Crystal Superalloy, PWA 1497, during High Temperature Creep Deformation

    pp. 336-339

    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.MB201003

    The microstructure stability of 4th generation single crystal superalloy, PWA 1497, during high temperature creep testing is discussed and compared with 2nd generation single crystal PWA 1484 superalloy. Quantitative scanning- and transmission electron microscopy methods are used to characterize the alloy microstructure and its changes during creep deformation at 980°C, especially the formation and subsequent directional coarsening of γ′ precipitates. The results show that the rafting parameter R is a suitable and reliable quantitative measure of the developed rafting.
  • Crystallographic Orientation Relationship between Discontinuous Precipitates and Matrix in Commercial AZ91 Mg Alloy

    pp. 340-344

    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.MB201021

    Discontinuous precipitates (DPs) have a random distribution at grain boundaries in commercial AZ91 Mg alloy, whereas continuous precipitates exist in the matrix. Previous studies have mainly focused on continuous precipitates and their orientation relationship with the matrix. In this study, thin cross sections of DPs in commercial AZ91 magnesium alloy aged at 489 K were prepared by focused ion beam milling. Their morphologies and the orientation relationship between the DPs and the matrix were investigated by transmission electron microscopy. The results reveal that the DPs have the shape of platelets. Selected-area electron diffraction patterns of the DPs allowed them to be identified as β-Mg17Al12. The DPs were found to have the same orientation relationship (i.e., Burgers, Potter or Crawley) as the continuous precipitates in the matrix. However, their longitudinal directions were not fixed, but were distributed about their (11\\bar1) zone axis.
  • Interface Reactions between Conductive Ceramic Layers and Fe-Cr Steel Substrates in SOFC Operating Conditions

    pp. 345-351

    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.MB201013

    To improve contact resistance and protect the cathode from chromium poisoning, perovskite (La,Sr)CrO3, (La,Sr)CoO3 and spinel MnCo2O4 coatings were applied onto the surfaces of Fe-25Cr (DIN 50049) steel by means of the screen-printing method. The oxidation process of the coated steels under cyclic-oxidation conditions showed high compactness of the protective layer, good adhesion to the metal substrate, as well as acceptable area specific resistance level for SOFC metallic interconnect materials, which was the result of the structural modification of the coating/steel interface reaction, i.e. the formation of an intermediate, chromia-rich multilayer between the conductive coating and the metal substrate. The cross-sectional morphology and nanostructure of interface products formed during long-term thermal oxidation in air and the H2/H2O gas mixture at 1073 K were characterized using SEM-EDS and conventional TEM-SAD. Cr-vaporization tests showed that the perovskite and spinel coatings may play the role of barriers that effectively decrease the volatilization rate of chromia species.
  • The Early Stage of Dislocation Process around a Crack Tip Observed by HVEM-Tomography in Silicon Single Crystals

    pp. 352-357

    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.MB201024

    Crack tip dislocations in silicon single crystals were observed by combining high-voltage electron microscopy and electron tomography. Cracks were introduced by an indentation method and dislocations were introduced around the crack tip by keeping the indented sample at high temperatures for several hours. The number of dislocations emitted from the crack tip was controlled by changing the holding time of the indented specimen at high temperatures. The dislocations observed were characterized in detail. It was found that primary emitted dislocations all had the same Burgers vectors and that some dislocation segments cross-slipped around the crack. The local stress intensity factor due to dislocations was calculated, basing on the dislocation character obtained in this study, indicating that emitted dislocations shields mode I, II and III stress intensity at the crack tip. After the emission of the number of those dislocations, dislocations with another Burgers vector were emitted around the crack. It was found that those dislocations accommodate mode II and III stress components which are the excess shielding fields due to the dislocations primary emitted from the crack tip.
  • Effect of Internal Strain on Martensitic Transformations in NiTi Shape Memory Alloys

    pp. 358-363

    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.MB201012

    The analysis of the influence of precipitation processes as well as dislocation structure on the transformation course and its characteristic parameters in NiTi shape memory alloys was carried out. In order to describe structural changes caused by thermo-mechanical treatment, transmission electron microscopy technique was applied; the study included in situ observations during cooling and heating the specimen in the microscope. The structural changes were related to the evolution of the martensitic transformation determined from the differential scanning calorimetry (DSC) measurements. It was found that the non-homogeneity of stress fields caused by presence of coherent precipitates or by specific dislocation structure results in a multi-stage martensitic transformation. The transformation is preceded by the R-phase transition. Also this transformation can occur in many stages. A thermodynamical model of the multi-stage martensitic transformations occurring in the two-component NiTi alloys was elaborated, which allows anticipation of the transformation sequences in these alloys.
  • Electron Microscopy Studies of Non-Local Effects’ Impact on Cathodoluminescence of Semiconductor Laser Structures

    pp. 364-369

    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.MB201007

    Spatially and spectrally resolved cathodoluminescence (CL) studies performed in a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM) are widely applied to determine the luminescence spectrum, map the optical activity and reveal defects in semiconductor structures. It is commonly recognized that the CL signal represents the local properties of the structure region excited by the electron beam. The present investigations show that if the structure under study contains regions with a strong electric field (e.g. p-n junction), the CL signal may much depend on phenomena far from the excitation region. The range of CL-results distortion extends from negligible changes to completely wrong output. It depends on various parameters described in the paper. The CL results obtained for AlGaAs/GaAs laser heterostructures with InGaAs quantum well are presented.
    x

    Readers Who Read This Article Also Read

    1. Effect of Internal Strain on Martensitic Transformations in NiTi Shape Memory Alloys MATERIALS TRANSACTIONS Vol.52(2011), No.3
    2. Characteristics of Resistance Spot Welding for 1 GPa Grade Twin Induced Plasticity Steel MATERIALS TRANSACTIONS Vol.53(2012), No.11
    3. Structural Modification of Chalcopyrite Ore for Enhanced Copper Recovery MATERIALS TRANSACTIONS Vol.53(2012), No.11
  • Structural and Magnetic Properties of Co2FeAl0.5Si0.5 Full-Heusler Alloy Thin Films on GaAs Substrates

    pp. 370-373

    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.MBW201004

    We investigated the structural and magnetic properties of Co2FeAl0.5Si0.5 (CFAS) thin films on GaAs substrates. The CFAS thin films grew epitaxially on GaAs with CFAS (100)[100] || GaAs (100)[100] relation and formed an ordered L21 structure with substrate heating deposition at TSUB=300°C, 400°C and post annealed at TPA=400°C. Moreover, we confirmed the no reaction between CFAS and GaAs. The CFAS thin films on GaAs showed strong uniaxial magnetic anisotropy with an easy axis of [110]CFAS ([110]GaAs) direction and the magnetic anisotropy generally increased by decreasing the thickness of CFAS. The magnetic moment of the CFAS film deposited with substrate heating at 300 °C was approximately 4.8 μB/f.u. at room temperature.
  • X-ray Diffraction Study of the Ordered Structures and Phase Relation in Pd-Mn Alloy System

    pp. 374-379

    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.M2010372

    This paper reports the results of structural study on the ordered phases formed in Pd-rich Pd-Mn alloys adopting X-ray powder diffraction method. Formations of the tetragonal D023-type Pd3Mn, orthorhombic Pd2Mn and orthorhombic Pd5Mn3 reported by previous researchers have been confirmed. Rietveld refinement of the diffraction data of the latter two phases has determined precisely the atomic parameters and revealed the significance of the shifts of atoms in Pd2Mn. It is shown that the L10-type phase extends to about 33 at% Mn at high temperatures and Pd2Mn and Pd5Mn3 form via two-step ordering from the L10-type phase. A revised phase diagram on the Pd-rich side has been proposed. Discussion is given on the stability of the relevant ordered phases by making calculation of the total energy by the density functional method.
  • Near-Surface Nanocomposite Structure on Commercial Purity Aluminum Induced by Fine Particle Bombardment

    pp. 380-385

    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-M2010827

    Commercial purity aluminum (A1070) was subjected to fine particle bombardment (FPB) with 1.0 mass% carbon steel and pure nickel projectile particles. Nanocomposite structures formed at the near-surface region, which contained refined aluminum grains of less than 100 nm in diameter and dispersed projectile fragments several tens of nanometer to several micrometer in size. Beneath the nanocomposite structure was found a fine-grained matrix with approximately 1-μm-diameter grains.
    Observation of the microstructural transition at the near-surface region suggested that the nanocomposite structures developed via severe plastic deformation (SPD), accompanied by a folding and imposing of the convex part of the surface, and by mechanical mixing with the fragments of the projectile particles.
    The nanocomposite structures exhibited high hardness values of approximately HV200, which are superior to those of extra-super duralumin (A7075-T6). The relationship between the grain size and hardness value in the structures corresponds well to the Hall–Petch relationship extrapolated from previous studies. Therefore, the increase in hardness is thought to be mainly the result of grain refinement strengthening.
  • Solidification of High Chromium White Cast Iron Alloyed with Vanadium

    pp. 386-390

    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.M2010059

    Experimental results indicate that vanadium affects the solidification process in high chromium iron. Vanadium is distributed between eutectic M7C3 carbide and the matrix, but its content in carbide is considerably higher. Also, this element forms vanadium carbide. TEM observation reveals that vanadium carbide present in examined Fe-Cr-C-V alloys is being of M6C5 type. DTA analysis found that with increasing vanadium content in tested alloys, liquidus temperature is decreasing, while eutectic temperature is increasing, i.e. the solidification temperature interval reduces. The narrowing of the solidification temperature interval and the formation of larger amount of vanadium carbides, as a result of the increase in the vanadium content of the alloy, will favour the appearance of a finer structure. In addition, the phases volume fraction will change, i.e. the primary γ-phase fraction will decrease and the amount of M7C3 carbide will increase.
  • On-the-Fly Kinetic Monte Carlo Simulation of Atomic Diffusion in L10 Structure

    pp. 391-396

    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.MBW201015

    The atomic diffusion in L10 ordered phase is investigated using on-the-fly kinetic Monte Carlo simulations. We construct a simple model system of L10 ordered phase. Although a simple model system is employed, the simulation results reveal quite complex aspects of the atomic diffusion. It is found that the activation energies of both constituent atoms change significantly depending on the composition and that the correlation factor makes the activation energy larger for both atoms. It is also demonstrated that the diffusion anisotropy in the L10 phase which is observed in the experiment is reproduced. We discuss the different diffusion behavior of the constituent atoms, and clarify the mechanism of the diffusion anisotropy in L10 phase.
  • Dynamic Behavior Evaluation of Martensitic Transformation in Cu-Al-Ni Shape Memory Alloy Using Acoustic Emission Simulation by FEM

    pp. 397-405

    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.M2010360

    Acoustic emission is defined as the ultrasonic wave phenomenon due to rapid release of strain energy in the solid materials. This paper aims at the extension of acoustic emission method for certain and effective analysis that can adapt to material research field. The rise time of two kinds of martensitic transformation in Cu-Al-Ni shape memory alloy, the β1 to β1′ and the β1 to γ1′ phase transformation, were observed by acoustic emission monitoring and the analysis based on the simulation of acoustic emission wave utilizing finite element method. In the simulation on finite element method, we considered the acoustic emission wave with the effect of inclined source such as the martensitic habit plane, source location in thickness direction of the specimen and rise time of acoustic emission source as the dynamic behavior. We found that the particular frequency range of zeroth-order mode Lamb wave has the differences only due to rise time of acoustic emission source. Finally we analyzed the rise time of two kinds of martensitic transformation with reviewing the results of simulation. As the result, the β1 to β1′ phase transformation showed the longer rise time than the β1 to γ1′ phase transformation in the nucleation step. It is thought that there is the difference between 18R and 2H periodic stacking order structure of martensite.
  • The Effect of Preheating on Notched Tensile Strength and Impact Toughness of Ti-6Al-6V-2Sn Laser Welds

    pp. 406-411

    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.M2010281

    Notched tensile strength (NTS) and impact toughness were determined for Ti-6Al-6V-2Sn laser welds subjected to post-weld heat treatment (PWHT) at distinct temperatures. In this study, the specimens were either preheated at 300°C or maintained at room temperature before laser welding. The preheated weld, associated with a reduced cooling rate, had obviously lower hardness than the non-preheated weld in the as-welded condition. After PWHT at 482°C for 3 h, the preheated weld also exhibited considerably lower hardness than the non-preheated weld. In general, preheating at 300°C could effectively increase the NTS and impact toughness of Ti-6Al-6V-2Sn laser welds. The preheated weld in the as-welded condition had superior NTS to other welds being tested. On the other hand, the welds after PWHT at 704°C possessed the best resistance to unstable impact fracture, regardless of preheating. Usually, the coarse α+β structures together with intergranular α were responsible for the high NTS and impact toughness of the weld.
  • Synthesis and Properties of Carbon Short Fiber Reinforced ZrCuNiAl Metallic Glass Matrix Composite

    pp. 412-415

    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.M2010028

    Carbon short fiber reinforced Zr50.5Cu36.45Ni4.05Al9 metallic glass matrix composite was synthesized. The microstructure, thermal behavior, and compressive property of composite are investigated. The improvement of thermal stability and Young’s modulus are due to the addition of short carbon fiber. The limited reaction occurs between the matrix and short fiber by reducing the reactive time, and only a ZrC reaction zone with about 150 nm in width forms. Such interfacial reaction can improve the wettability and tighten the bonding at the interface, and consequently enhance the strength of composite. The effect of interfacial reactive production on the compressive property is also discussed.
  • Thermodynamics of Inclusion Formation and Its Influence on the Corrosion Behavior of Cu Bearing Duplex Stainless Steels

    pp. 416-422

    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.M2010355

    To elucidate the thermodynamics of inclusion formation and its influence on the corrosion behavior of Cu bearing duplex stainless steels, potentiodynamic and potentiostatic polarization tests, a SEM-EDS analysis of inclusions, and thermodynamic calculations of the formation of inclusions were carried out. While the resistance to general corrosion of the noble copper contained alloy-1.5Cu in a deaerated 2 M H2SO4 was higher than that of the alloy-BASE, the resistance to pitting corrosion of copper contained alloy-1.5Cu in a deaerated 0.5 N HCl + 1 N NaCl and 30 mass% NaCl was lower than that of the alloy-BASE due to an increase of interface areas between inclusions and matrix acting as preferential pit initiation sites. The thermodynamic calculation for the formation of Cr-containing oxide inclusions was in good agreement with the experimental results.
  • Effects of Implanted Deuterium on In-Situ Irradiation Fatigue Behaviors of Cold-Worked 316 Stainless Steel at 60 and 300°C

    pp. 423-427

    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.MBW201014

    Stress-controlled fatigue tests were performed for 20% cold-worked 316 stainless steel under in-situ 10 MeV deuteron irradiation with an energy degrader at 60 and 300°C. The irradiation dose rate and the deuterium implantation rate were arranged in response to beam intensity in three conditions as (A) 1.0×10−7 dpa/s and 1.1×10−3 appm/s, (B) 5.0×10−7 dpa/s and 5.5×10−3 appm/s and (C) 1.0×10−6 dpa/s and 1.1×10−2 appm/s, respectively. The number of fatigue cycles to fracture (NF) increased with the dose rate in order of conditions (A), (B) and (C) at 300°C, while NF was lower in condition (C) than that in condition (B) irrespective of the higher dose rate at 60°C. Although transgranular cracking in the ductile fracture mode was indicated on fracture surface for all specimens, higher density of dimples was formed for the in-situ irradiation specimen in condition (C) at 60°C. Some evidence of effects of implanted deuterium on in-situ irradiation fatigue behavior were demonstrated in this paper.
  • Minimization of the Free Energy under a Given Pressure by Natural Iteration Method

    pp. 428-432

    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.MBW201011

    Natural iteration method within the Cluster Variation Method is coupled with zero potential to minimize the free energy under the constraint of a constant pressure. The calculated results reproduce the ones obtained by the conventional method in which a gradient of the free energy curve is estimated at each atomic distance. It is noted that the computation time is much reduced in the present scheme and, therefore, it has a potential applicability in the future calculations with a free energy containing a larger number of variables.
  • High Temperature Corrosion of CoNiCrAlY-Si Alloys in an Air-Na2SO4-NaCl Gas Atmosphere

    pp. 433-438

    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.MBW201026

    The addition of Si to CoNiCrAlY was considered in order to develop corrosion resistant alloys for coating applications. The high temperature corrosion behavior of spark plasma sintered CoNiCrAlY alloys of 0, 10, 20, and 30 mass% Si content was investigated in an air-(Na2SO4+25.7 mass%NaCl) gas atmosphere at elevated temperatures of 923, 1073, and 1273 K. The results showed that CoNiCrAlY-Si alloys formed mainly an Al2O3 or Al2O3/SiO2 scale, depending on the alloy composition and the temperature. The addition of 30 mass% Si significantly improved the high-temperature corrosion resistance of CoNiCrAlY alloy in an air-(Na2SO4+25.7 mass%NaCl) gas atmosphere at these temperatures. The high temperature corrosion behavior of CoNiCrAlY-Si alloys was discussed in the present paper.
  • Observation of High Resolution Microstructures in Thermal Sprayed Coatings and Single Deposited Splats Using Ion Beam Milling

    pp. 439-446

    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.T-M2010826

    We have investigated microstructures of thermal sprayed coatings and single deposited splats using two types of ion beam milling: one is broad argon ion beam for the cross-sectioning of thermal sprayed coatings in a cross section polisher and the other is focused gallium ion beam for the cross-sectioning and transmission electron microscopy (TEM) sample preparation of single splats. The cross section of tungsten carbide-cobalt (WC-Co) coatings fabricated by the polisher showed that it created a mirrored surface with minimized artifacts such as pull-outs of ceramic particles or smearings of pores which can be made by conventional metallographic preparations. A thin and locally re-thinned membrane of single nickel (Ni) splat was feasible to observe the internal interface of particle/substrate in high resolution atomic scale images. Substrate was heavily deformed by the impact of nickel particle with high kinetic and thermal energies. The particle and the substrate were intimately bonded without any voids or gaps.
  • Analysis of Shear Droop on Cut Surface of High-Tensile-Strength Steel in Fine-Blanking Process

    pp. 447-451

    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.P-M2010828

    The fine-blanking process is used in the production of automobile parts and other metal components. Although the fine-blanking process can produce sheared surfaces with higher precision than the punching process, shear droops on cut surfaces are also formed, as in the punching process. It is important to determine the causes of the formation of shear droops, but the mechanism is difficult to determine experimentally. Here, the finite element method (FEM) is adopted to study the causes of the formation of shear droops. The cut surfaces in the present experiments have fine sheared surfaces but no fracture surfaces. Although a combination of the fracture criterion and element-kill method is used for many simulations of the fine-blanking process, fine sheared surfaces cannot be evaluated by the combination of these methods. In the present calculations, an adaptive remeshing technique for FEM is used to create fine sheared surfaces. The shear droop is associated with the initial compression by and the subsequent clearance of the punches and dies. Results are obtained for various clearances and initial compressions in the fine-blanking process for high-strength steel, and the experimental and calculation results are compared. In the present paper, we show that the shear droops are affected by the clearance of and initial compression by the punches and die.
  • Reducing Work Load and Increasing Dimensional Accuracy in Parts for Bending of High-Strength Steel Sheets for Automobiles

    pp. 452-457

    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.F-M2010828

    In this paper, we propose a method suitable for increasing the dimensional accuracy in the bending of high-strength steel sheets with a small work load by controlling the amount of a punch indentation in V-bending. The optimal indentation for obtaining the desired bending angle exactly could be calculated by finite-element-method (FEM) simulation using many types of high-strength steel sheets with different material characteristics. This method is effective for reducing the work load and obtaining a small radius of curvature in bent steel sheets; thus, it is suitable for forming high-strength steel sheets, which have been used widely for the fabrication of automobiles.
  • Suppression of Crystallization in Ti-Based Alloys by Fluxing

    pp. 458-463

    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.MBW201001

    Controlling crystal nucleation and growth leading to formation of nano structures by an original flux treatment method mainly in calcia and magnesia crucibles followed by water-cooling allowed production of Ti45Cu45Fe10 bulky nanostructured alloy of 16 mm in diameter. Since a glass forming ability (GFA) of the alloy composition is low, the alloy could not form an amorphous structure even by a common rapid quenching manner such as a melt-spun method. At the same time control over crystal nucleation and growth by fluxing was achieved on melting with flux—a reagent which has a low melting temperature and good wettability. The crystal growth control in our investigations is also possible for different other alloys such as Ti45Cu45Ni10 alloy.
  • Surface Analysis of Electrochromic Switchable Mirror Glass Based on Magnesium-Nickel Thin Film in Accelerated Degradation Test

    pp. 464-468

    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.MBW201010

    With the capability to change between reflective and transparent states, electrochromic switchable mirrors are expected to have numerous applications in optical devices, electronics devices and new energy-saving windows. If conventional windows can be adapted to incorporate switchable mirror technology, the solar radiation coming into a room could be effectively controlled, owing to features of the reflective state. Conventional windows are often subjected to environmental conditions such as high temperature and humidity. Considering practical use, we investigated the effects of the environment on the optical switching properties of the device in accelerated degradation tests using a thermostat/humidistat bath at a constant temperature of 313 K and constant relative humidity of 80%. When the device was kept in the bath for 950.4 ks, it lost its optical switching properties. This result was associated with the degradation of the surface layer of the Mg4Ni thin film, which became rougher with increasing bath duration. We confirmed that the layer contained species in non-metallic states of oxide and hydroxide. Furthermore, the degradation mechanism to form the mixture state depended on the holding time in the bath.
  • A Simple Model to Describe the Rule of Glancing Angle Deposition

    pp. 469-473

    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.M2010342

    A model was built to study the rule of glancing angle deposition. This model, which is called hemisphere model, is convenient to describe how the experimental conditions influence morphology of the nanostructures prepared by GLAD. Influence of experiment conditions such as incidence angle, incidence rate, substrate temperature, and substrate rotation rate are theoretical analyzed by the hemisphere model, and validated respectively by amount of experiments. As an application of the model, metals of different melting points were deposited into coherent multi-section nanorods by adjusting substrate temperature.
  • High Chromium Fe-Cr-Mo-P-C Amorphous Coating Films Produced by Thermal Spraying Technique

    pp. 474-480

    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.MBW201009

    High chromium Fe-Cr-Mo-P-C amorphous coating films containing up to about 35 at% Cr having high hardness and high corrosion resistance have been produced by a newly developed thermal spraying technique. In order to control the temperatures of the powder particles in the flame spray and the substrate, a cylindrical nozzle, with external cooling nitrogen gas, was mounted to the front end of the thermal spraying gun. Fe70Cr10P13C7 and Fe38Cr35Mo7P13C7 films with various external cooling gas velocities between 20 m/s and 40 m/s exhibited entire amorphous structure without oxides and/or unmelted powder particles. High corrosion-resistance of the Fe38Cr35Mo7P13C7 amorphous coating film was observed in immersion tests using 35% hydrochloric acid.
  • Decomposition of Magnesium Hydride Fiber Observed Using TEM and In-Situ AFM

    pp. 481-485

    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.MBW201021

    The thermodynamics and the decomposition behavior of an MgH2 fiber of a single crystal synthesized by chemical vapor deposition were investigated using in-situ atomic force microscopy and transmission electron microscopy. The MgH2 fiber without oxidation decomposed into polycrystalline Mg with a crystalline size of 20–50 nm. The polycrystalline Mg absorbed hydrogen at a pressure similar to the equilibrium pressure of bulk Mg. On the other hand, the MgH2 fiber with surface oxidation decomposed into Mg crystals larger than 100 nm. The surface oxide layer affected the decomposition behavior of the MgH2 fiber and prevented polycrystallization. These results suggest that surface oxidation increases the equilibrium pressure for hydrogen absorption of the MgH2 fiber.
  • Magnetic Properties of Nanoparticle–Polymer Composites Prepared Using Surface Modification and Cross-Linking Reaction

    pp. 486-490

    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.MAW201020

    Polymer composites of magnetic particles are widely used as microwave absorbers. An effective method for obtaining thinner microwave absorbers for device mounting is to increase the volume fraction of magnetic nanoparticles within the composites such that the permeability is enhanced. In this study, composites were prepared using magnetite nanoparticles surface-modified with 4-META (4-methacryloylioxyethyl trimellitate anhydride) and cross-linked with PEG-4SH (pentaerythritol tetra-polyethylene glycol ether with four thiol-modified terminals). These composites have a higher volume fraction of nanoparticles (up to 62 vol%) and higher permeability than conventional epoxy resin composites. In addition, the prepared composites showed good microwave absorption properties (R.L.<−20 dB) with a smaller matching thickness (d=8.0 mm) than the epoxy resin composites (d=9.0 mm).
  • Growth of Ti-Based Interface Layer in Cu(Ti)/Glass Samples

    pp. 491-497

    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.MBW201017

    Cu(Ti) alloy films with low-resistivity and excellent-adhesion have been successfully prepared on glass substrates. To gain further resistivity reduction and adhesion strength, growth of a Ti-based interface layer was investigated using Rutherford backscattering spectrometry (RBS) in the present study. Cu(0∼5 at%Ti) alloy films were deposited on glass substrates and subsequently annealed in vacuum at 400∼600°C for 0.5∼24 h. Results were compared with those for samples on SiO2 substrate previously obtained. Ti peaks were obtained in RBS spectra only at the interfaces for both Cu(Ti)/glass and Cu(Ti)/SiO2 samples. Molar amounts of Ti atoms segregated to the interfaces (n) were estimated from Ti peak areas. The m values estimated from the slopes of the logn versus logt lines were almost similar for all the samples (m=0.10∼0.12), suggesting that growth of the Ti-based interface layers was controlled by a similar mechanism. The activation energy of the Cu(Ti)/glass samples was similar to that of the Cu(Ti)/SiO2 samples, while a pre-exponential factor (Z) of the Cu(Ti)/glass samples was approximately half of the value of the Cu(Ti)/SiO2 samples. The Z value shows the frequency with which the Ti atoms meet oxygen in the glass substrates. Impurities in the glass substrates lowered the frequency. These factors lead to the conclusion that growth rate of the Ti-based interface layers on glass substrates was slower than that on SiO2. The Ti-based interface layer growth was also influenced by microstructure of Cu(Ti) alloy films formed on the glass substrates. Columnar grains in the Cu(Ti) alloy films were seen to enhance Ti segregation. However, an equiaxed zone above the interface retarded Ti diffusion to the interface, leading to lack of Ti atoms for the reaction.
  • Effects of CO2 Emissions Trading on Steel Scrap Recycling: A Simulation Analysis Using a Computable General Equilibrium Model

    pp. 498-506

    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.M2010289

    This study aims to examine whether the absolute amount of steel scrap used in Japan increases under an emissions trading scheme using an economic simulation model known as the computable general equilibrium model.
    This study’s computable general equilibrium model is a single-country, multi-sector model. An important feature of our model is that the iron and steel manufacturing sector is disaggregated in detail. The disaggregation is based on differences in production methods and types of steel products.
    In our simulation, although demand for electric arc furnace steel products in Japan increases in response to the implementation of emissions trading because of their low carbon intensity, the absolute amount of steel scrap used decreases. This is because the price substitution effect between electric arc furnace steel products and blast furnace–basic oxygen furnace steel products is dominated by the economic scale effect stemming from the negative economic impacts of emissions trading.
  • Effects of Hydrogen Diffusion on the Mechanical Properties of Austenite 316L Steel at Ambient Temperature

    pp. 507-513

    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.M2010273

    This study examined how the strain rate affects the room-temperature tensile behavior of hydrogen-charged 316L stainless steels. A high-temperature homogenization treatment was applied to the specimens after hydrogen charging and copper electroplating to remove the hydrogen concentration gradient. A softening phenomenon was observed in the hardening behavior of the H-charged and homogenized specimen at a strain rate of 2×10−3/s. The observation was further confirmed by an inspection of the fracture surface of the tensile test specimen.
  • Microstructural and Corrosion Characteristics of Iron-Silicon Alloyed Layer on 5083 Al Alloy by Electrical Discharge Alloying Processing

    pp. 514-520

    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.M2010363

    In the study, the surface modification of 5083 Al alloy by electrical discharge alloying (EDA) with a 75 mass% ferrosilicon electrode was used to examine the effects of machining parameters (discharge current, pulse duration and duty factor) on the thickness, hardness and surface roughness of the alloyed layer. Experiment results reveal that the thickness tends to increase with the increase in the pulse duration and discharge current. In addition, the micro-hardness evidently higher compared to the substrate. The hardness also increases with the increasing discharge current and pulse duration. TEM examinations show that the matrix of the alloyed layer is an amorphous-like structure, whereas the matrix contains fine needle-like Si particles, block-like Si particles and nano-size Al4.5FeSi and Al13Fe4 particles. The results of EPMA compositional analysis indicate that the alloying elements (Si and Fe) contained in the electrode effectively dissolve in the alloyed layer of 5083 Al alloy and the content of the dissolved alloying elements gradually decreases with the increase in the distance from the discharge surface. Furthermore, the surface roughness increases with the increase in the discharge current and pulse duration. It is also found that the alloyed layer with composite microstructures exhibits sufficient corrosion resistance to NaCl aqueous solutions.
  • Effect of Carbon on Spinodal Decomposition in Fe-26Mn-20Al-C Alloys

    pp. 521-525

    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.M2010255

    The supersaturated austenite (γ) phase decomposed into fine C-rich ordered k′ particles and C-depleted γ0 phase during quenching in alloys with 5.5≤C≤8.0 at%. The misfit between k′ particles and γ0 phase decreased with increasing carbon content. The strain energy increased dramatically as carbon content approached slightly below 5.5 at%. Undercooling may be insufficient to overcome the strain energy effects, thus leading to the absence of spinodal decomposition and k′ particles in the present and prior austenitic FeMnAlC alloys with 3.1≤C≤5.2 at% under the as-quenched condition. Additionally, both the amount of ordered k′ particles and the carbon concentration in the k′ particles increased with increasing carbon content of the alloy. These results revealed that a higher degree of carbon supersaturation in the initial γ phase might promote a tendency toward C-rich k′ particle formation during quenching.
  • Pressure-Composition Isotherms of TiC1−x–H System at Elevated Temperatures

    pp. 526-530

    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.M2010307

    Pressure-composition isotherms of TiC1−x–H system were measured at 773, 873 and 973 K over a pressure range from 10−2 to 105 Pa. The obtained isotherms could be divided in three concentration regions. In the low concentration region in which [H]⁄[TiC]≤1.4×10−3, Sieverts’ law held, and the solubility of hydrogen clearly increased with decreasing temperature. The enthalpy of solution was −70±5 kJ mol−1. In the region in which 1.4×10−3<[H]⁄[TiC]≤8.0×10−3, the dependence of hydrogen concentration, CH, on pressure and temperature weakened as pressure increased. Finally, CH was independent of temperature when it reached 8.0×10−3. This CH was comparable with the concentration of carbon vacancies in TiC1−x. In the high concentration region in which [H]⁄[TiC]≥8.0×10−3, Sieverts’ law held again, but the solubility of hydrogen was almost independent of temperature. These observations indicated that hydrogen dissolved in carbon vacancies in the low and middle concentration regions with the above-mentioned value of enthalpy of solution, and also occupied much less stable sites in the high concentration region.
  • On-Line Detection System for Internal Flaws in As-Hot-Rolled Steel Strip Using Ultrasonic Probe Array

    pp. 531-538

    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.M2010334

    A new ultrasonic immersion test method for detecting internal flaws in a running steel strip has been developed. A transmitting probe array and a receiving probe array are arranged face-to-face on opposite sides of the strip in water, and two flaw echoes are received by the receiving probe array: (1) Flaw echo reflected first at an internal flaw and next at the surface wall of the strip; and (2) Flaw echo reflected first at the back wall of the strip and next at an internal flaw. A linear area in the strip can be tested within a cycle of ultrasonic pulse repetition by integrating the transmission of a line-focused ultrasonic beam (25 MHz in frequency) using all elements in the transmitting probe array at once with the parallel processing of signals received by the receiving probe array. An ultrasonic detection system based on this method was subsequently installed in the No. 6 pickling line at JFE Steel, Chiba District. The steel strip being tested is immersed in water by using six additional deflector rolls. The transmitting probe array and receiving probe array cover the width of the strip so that testing of the entire volume of the strip is realized. It is confirmed that inclusions with a minimum volume of 5×10−5 mm3 can be detected at a signal-to-noise ratio in the range of 9–10 dB. The detection results are rapidly fed back to the steelmaking process to improve steel cleanliness. As a result, steel coils have maintained a high level of internal cleanliness with a dramatic reduction in defects found during the users’ manufacturing process.
  • Ultrasonic Method for Testing Spot-Welds

    pp. 539-546

    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.M2010336

    We developed a technique for nondestructively evaluating spot-welds based on through-transmission of Lamb waves. The nugget diameter can be evaluated by measuring the width of the zone where attenuated transmitted waves are observed. A particularly important feature of the developed technique is that spot-welds with no weld metal can be reliably distinguished from spot-welds with weld metal. We also developed a measuring system using array transducers. The measurement results using the system agree well with the nugget diameters measured by cross-sectional observation.
  • Comparison of Theoretical Models of Electron-Phonon Coupling in Thin Gold Films Irradiated by Femtosecond Pulse Lasers

    pp. 547-553

    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.M2010396

    This study reports on a comparison of theoretical models for electron-phonon coupling that is substantially associated with non-equilibrium energy transport in thin gold films irradiated by femtosecond pulse lasers. Three published electron-phonon coupling models were analyzed with the use of a well-established two-temperature model to describe non-equilibrium energy transport between electrons and phonons. Based on the numerical results, at lower fluence, all models showed nearly similar tendencies, whereas at higher fluence, constant electron-phonon coupling forced unrealistically long electron-phonon equilibration times and spatially long diffusive regions as it failed to intrinsically consider the effect of a high number density of excited d-band electrons. Even at higher fluence, however, both Lin’s and Chen’s models yielded physically reasonable results, showing converging electron-phonon equilibration times and steep gradients in the spatial lattice temperature profiles at higher laser fluence. In particular, Lin’s model predicts nonlinear characteristics of heat capacity and lattice temperature with respect to laser fluence better than Chen’s model. Moreover, the electron-phonon relaxation time increased with laser fluence, whereas at laser fluence greater than 0.05 J/cm2, the thermal equilibrium time was nearly independent of the laser fluence. Thus, it was concluded that Lin’s model better predicted the electron-phonon coupling phenomena in thin metal films irradiated by ultra-short pulse lasers.
  • Polycrystalline TiO2 Thin Films with Different Thicknesses Deposited on Unheated Substrates Using RF Magnetron Sputtering

    pp. 554-559

    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.M2010358

    Different film thicknesses of polycrystalline TiO2 thin films deposited on various unheated substrates using radio frequency (RF) magnetron sputtering is investigated. The crystalline structure, optical properties, and surface morphology and roughness were measured using an X-ray diffractometer (XRD), a field-emission scanning electron microscope (FESEM), an atomic force microscope (AFM), and a UV-Vis spectrophotometer. Polycrystalline phases were formed on unheated substrates due to the plasma particle bombardment. Crystalline structures more easily formed on the glass substrate and only nanocrystalline structures formed on the ITO glass substrate due to the surface roughness of substrates. The absorption edge and optical band gap depended on the crystalline particle size and phase structure. The XRD results indicate that 500-nm-thick film on a glass substrate had the strongest intensities of mixed anatase and rutile phases.
  • The Microstructure and Wear Properties of Laser-Clad WC-Cr3C2 Cermet Coating on Steel Substrate

    pp. 560-563

    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.M2010410

    WC-Cr3C2 cermet coating on carbon steel was fabricated by laser controlled reactive synthesis and exhibited the metallurgical bonding at the interface between coating and substrate. The microstructure and wear properties of laser-clad WC-Cr3C2 Cermet Coating on steel substrate have been investaged by means of scaning eletron microscopy (SEM), X-ray diffraction (XRD), microhardness testing and wear testing. Experimental results show that the coating has a very good thermal resistance and high bonding strength due to Ni addition, which decreases stress concentration at the interface and increases the bonding strength due to better wettability. The coating shows superior hardness and wear resistance. In the same wear conditions, the wear resistance of the coating is 4 times than that of steel substrate.
  • Thermal Conductivity and Interconnectivity of Hexamethylene Diisocyanate Contained Polyurethane Grafted Multiwall Carbon Nanotube/Polyurethane Nanocomposite Film

    pp. 564-567

    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.M2010322

    The hexamethylene diisocyanate (HDI) contained polyurethane (PU) grafted multi-walled carbon nanotubes (HDI-g-MWNTs) have been synthesized by simple blending method to fabricate thermal conductive nanocomposite. This method shows that HDI-g-MWNTs can improve the interfacial compatibility between HDI-g-MWNTs and matrix. The HDI base PU thermal conductive film (HDI-PU) showed enhanced dispersibility of functionalized MWNTs because of low crystallinity which was affected by its steric hindrance. The length of MWNTs was prevented until the end of the reaction. The long distance of MWNTs could be help to make good thermal conducting path. These phenomena have influence on the excellent thermal conductivity. The thermal conductivity increased from κ=0.274 W/mK to κ=0.645 W/mK, as the addition of the MWNTs increase to 1.2 vol%. The interconnectivities of HDI-Polyurethane have higher value than other composite films.
  • Reactive Transient Liquid Phase Bonding between AZ31 Magnesium Alloy and Low Carbon Steel

    pp. 568-571

    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.M2010359

    A new liquid-phase bonding method was developed to establish a strong bonding between Al bearing Mg alloys and steels by intentionally forming a thin and uniform reaction layer at the bonding interface. By adopting Ag as an interlayer between the Mg alloys and steel, Mg-Ag eutectic melt is produced at 773 K and nano-scale Fe-Al reaction layer is uniformly formed at the melt-steel interface during the isothermal solidification of the melt which is driven by the diffusion of Ag into the Mg alloy. At the completion of the solidification, exceptionally strong bonding, exceeding the yield strength of the base Mg alloys, is achieved.
  • Alignment of Carbon Nanofibers in the Al2O3 Matrix under a Magnetic Field

    pp. 572-575

    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.M2010326

    A stable suspension of multi-walled carbon nanofibers (CNFs) in Al2O3 was prepared by adding ammonium polycarboxylate as a dispersant in an aqueous solution. A strong magnetic field of 12 T was applied to the CNFs/Al2O3 suspension to investigate the alignment of the CNFs. The result was that the CNFs in the matrix showed good alignment with the direction of the magnetic field. It was found that 0.5 mass% CNFs showed isolated alignment; in contrast, with 5 mass% CNFs there were mainly aligned bundles. The alignment was only seen with straight CNFs; curved CNFs showed no alignment in a magnetic field.
  • Effect of Cracking on Mass Transport of Building Materials

    pp. 576-579

    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.M2010377

    The influence of crack due to freeze-thaw cycles on the mass transport of concrete materials has been studied. Different degree of cracking was produced by different freeze-thaw cycles. The mass loss of the concrete specimen after different cycles was chosen as the main parameter to describe the cracking state. Carbonation and chloride diffusion test were carried out. Results indicated that both of the carbonation depth and the chloride penetration rate were increased due to the internal cracking of materials. The more serious the concrete was damaged, the greater was the carbonation depth and the chloride migrate coefficient.
  • Effect of Pulse Frequency on Corrosion Behavior of AZ91 Mg Alloy Treated by Microarc Discharge Oxidation Coating

    pp. 580-583

    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.M2010395

    The paper demonstrated the anti-corrosion properties of an AZ91 Mg alloy fabricated via microarc discharge oxidation under an AC condition with various pulse frequencies ranging from 60 Hz to 2000 Hz. The structural features and phase compositions of the coating layers were characterized by utilizing scanning electron microscope and X-ray photoelectron spectroscopy. The optimum frequency for the coating layers with thick, uniform thicknesses was found to be 500 Hz for the conditions used in this study. This fact was explained by the change in the mode of spark discharge during coating, resulting in the occurrence of surface cracks as well as the transformation of Mg(OH)2 to MgO. Potentio dynamic polarization tests in 3.5 mass% NaCl solution revealed that the sample coated at a frequency of 500 Hz exhibited a corrosion potential of −1.42 V (vs. Ag/AgCl), suggesting a better corrosion resistance as compared to the other conditions.

Article Access Ranking

16 Jun. (Last 30 Days)

  1. Perspective toward Long-term Global Goal for Carbon Dioxide Mitigation in Steel Industry Tetsu-to-Hagané Vol.105(2019), No.6
  2. A Kinetic Model of Mass Transfer and Chemical Reactions at a Steel/Slag Interface under Effect of Interfacial Tensions ISIJ International Vol.59(2019), No.5
  3. Effects of Surface Microstructure on Selective Oxidation Morphology and Kinetics in N2 + 5%H2 Atmosphere with Variable Dew Point Temperature ISIJ International Vol.59(2019), No.5
  4. Improvement of Sinter Strength and Reducibility through Promotion of Magnetite Ore Oxidation by Use of Separate Granulating Method ISIJ International Vol.59(2019), No.5
  5. Evaluation of the Structure and Strength of Coke with HPC Binder under Various Preparation Conditions ISIJ International Advance Publication
  6. Effect of Nut Coke Addition on Physicochemical Behaviour of Pellet Bed in Ironmaking Blast Furnace ISIJ International Vol.59(2019), No.5
  7. Internal Friction Behavior Associated with Martensitic Decomposition in Low-carbon Dual-phase Steel ISIJ International Advance Publication
  8. Numerical Investigation of Applying High-carbon Metallic Briquette in Blast Furnace Ironmaking ISIJ International Vol.59(2019), No.5
  9. Evolution Mechanism of Inclusions in H13 Steel with Rare Earth Magnesium Alloy Addition ISIJ International Advance Publication
  10. Solidification Structure, Non-metallic Inclusions and Hot Ductility of Continuously Cast High Manganese TWIP Steel Slab ISIJ International Vol.59(2019), No.5

Search Phrase Ranking

16 Jun. (Last 30 Days)

  1. blast furnace
  2. blast furnace permeability
  3. blast furnace productivity
  4. deadman coke
  5. inclusions
  6. a structurally-based viscosity model of the fully liquid slags in the cao-mgo-al2o3-feo-sio2 system
  7. bubbling ladle
  8. feni + refining
  9. isij xafs
  10. joo hyun park