Using thermodynamic data obtained over a wide range of temperatures, a thermodynamic assessment of the Ni–Zr system was carried out. The associated solution model was applied to describe the short range ordering in the liquid, and the glass transition was treated as a second order transition, using the Hillert–Jarl functions. The driving force of crystallization, and the time–temperature–transformation (TTT) curves were estimated from the optimized parameter set, and compared with experimental data and the results of previous thermodynamic assessments. Taking into account the low temperature thermodynamic data, the calculated driving force was found to have decreased compared to the previous assessments. Consequently, the nose of the TTT curve was shifted to higher times.

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Iron-rich Fe₅₀Nd_50−xAl_x (x=5, 10, 15, 20 at%) alloys were produced by copper mold casting and melt-spinning in order to examine the formation of amorphous alloys. The bulk amorphous cylinders with diameters up to 1.5 mm have been obtained for the Fe₅₀Nd₃₅Al₁₅ alloy. The crystallization temperature (T_x) and melting temperature (T_m) of the alloy are 774 and 880 K, respectively. Accordingly, the temperature interval of T_m and T_x, ΔT_m (=T_m–T_x), is calculated to be 106 K, and the reduced crystallization temperature (T_x⁄T_m) is 0.88. The small ΔT_m and high T_x⁄T_m values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Fe–Nd–Al alloy. The bulk amorphous cylinder exhibits semi-hard magnetic properties at room temperature, i.e., 0.117 T for remanence and 50 kA/m for intrinsic coercive field for Fe₅₀Nd₃₅Al₁₅ alloy with a diameter of 1.5 mm. Moreover, soft to hard magnetic transition between the ribbon and bulk specimens was observed in the Fe-rich Fe–Nd–Al alloys. The semi-hard magnetic properties for the Fe-rich Fe–Nd–Al amorphous alloys with high amorphous-forming ability are promising for future progress as a new type of Fe-based magnetic material.

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The dependence of the glass transition on the local volumetric strain of each atom has been shown by Egami and others. The atomistic strain defined by the deformation tensor of the Voronoi polyhedra exhibits a different tendency from that of the total strain of the whole system. Even below the glass transition temperature, some percent of the atoms have strains that are already over the critical strain predicted by theory. In addition, the atomic deviatoric distortion has a non-zero value, while the total deviatoric distortion remains zero at the glass transition in the heat cycle. In this paper, the strain states at the glass transition, such as the volumetric strain and deviatoric distortion, are investigated for Cu and Zr based amorphous metals with three different compositions. We found that the local glass transition depends on the deviatoric distortion of atoms and, in these cases, starts at 600 K, a lower temperature, than that of the global glass transition at 1100 K.

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The establishment of appropriate machining techniques for bulk metallic glasses (BMGs), which exhibit excellent mechanical, physical and chemical properties, is required to apply the BMGs. In this report, the cutting characteristics of BMGs were examined by turning with different tool materials, nose radii (R_n) and cutting speeds (V). Round bars of Zr₆₅Cu₁₅Ni₁₀Al₁₀ and Pd₄₀Cu₃₀Ni₁₀P₂₀ at% BMGs were used as the workpieces. In order to compare the cuttability of the BMGs with that of crystalline alloys, steel (JIS SGD-400D) and free-cutting brass (JIS C3604) were used. The principal cutting force (F_H) and surface roughness (R_a) of the machined surfaces were measured. X-ray diffraction patterns were also obtained from the machined surfaces. The value of R_a in the BMGs exhibit the upper end of precise finishing level (i.e., R_a=0.2 μm), and was remarkably lower compared with the steel and a little lower compared with the free-cutting brass in spite of the value of V. The value became smaller with increasing values of R_n, exhibiting a very low value of 0.08 μm for an R_n value of 1.2 mm. The values of F_H in both BMGs did not show a clear difference and were half that of the steel for a V value less than 40 m/min, even though the tensile strength of the BMGs was twice as large as the steel. The chip of the BMGs showed an ideal flow type with very short and regular intervals, formed by planar slip, and revealed very homogeneous, flat and featureless back surfaces. From these observations of chips, it is presumed that the reason for the excellent cuttability of BMGs is due to a slipping-off mechanism at planes of very short intervals decided only by the maximum shear stress and non-built-up edges caused by a low glass transition temperature.

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The effect of the microstructural change on the high-temperature tensile deformation behavior in the supercooled liquid region is investigated in the pre-annealed Zr₆₅Al₁₀Ni₁₀Cu₁₅ bulk metallic glass. The microstructure before the tensile test on the specimen annealed at 673 K for 1.8 ks shows that a small amount of icosahedral phase precipitates and a large amount of amorphous phase still remains. On the contrary, the specimen annealed at 673 K for 2.7 ks shows that a large amount of icosahedral phase precipitates and the presence of amorphous phase is hardly noticeable. From the fact that flow stress of the specimen annealed at 673 K for 2.7 ks increases in comparison with that of as-received specimen as well as the specimen annealed at 673 K for 1.8 ks in the tensile test, it seems that the deformation behavior in the tension tests is greatly influenced by the difference in the degree of the precipitation of icosahedral phase. Since the m value is about 0.5 and many grain boundaries of icosahedral phase are formed in the specimen annealed at 673 K for 2.7 ks, the interaction between the icosahedral phase particles must be the cause of increase in initial stress. Accordingly, the microstructure of the gage section after tensile test in the specimen annealed at 673 K for 1.8 ks shows that the large amount of icosahedaral phase precipitates in the amorphous matrix. The strain hardening must be caused by the interaction between the icosahedral phase particles whose precipitation and growth are enhanced by deformation.

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In this work, the characteristics of shear bands and fracture surfaces of Zr₆₅Al_7.5Ni₁₀Pd_17.5 bulk metallic glass fractured by a tensile test was investigated. Zr₆₅Al_7.5Ni₁₀Pd_17.5 bulk metallic glass shows a yield stress of approximately 1.3 GPa, a fracture stress of approximately 1.5 GPa and a tensile plastic strain of 0.1–0.2% irrespective of the applied strain. Wavy, meandering shear bands were observed in the relatively wide area of specimen surfaces around the point of failure, and typical vein patterns were observed on the fracture surfaces. Shear bands and fracture surfaces were further examined by confocal microscopy to obtain more precise information on their roughness. On the other hand, evidence of viscous flow due to crack propagation was also obtained around the edge at the point of failure on specimen surfaces by confocal microscopy. The deformability of Zr₆₅Al_7.5Ni₁₀Pd_17.5 bulk metallic glass is discussed on the basis of the obtained results.

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In this study, the nanoscopic deformation behavior in single amorphous during loading-unloading process under tensile and shearing stresses were analyzed by the molecular dynamics method and were compared with the earlier experimental results where an anelastic behavior was not shown in tensile stress but in shearing stress. In this study a clear anelastic deformation was shown in the shearing stress. However, it didn’t occur in the tensile stress. This corresponds to the earlier experimental result. When an abrupt strain increase in the stress–strain curve was exhibited, the potential energy and atomic volume has been increased suddenly. This result indicates that the anelastic response of the amorphous metal in the shearing stress was generated by local phase transformation.

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Although pre-crystallization phase separation was reported in the Al₈₈Gd₆Er₂Ni₄ amorphous alloy, this work has found no evidence for it. Surface crystallization was found to occur prior to the major crystallization of α-Al nanocrystals, which caused uneven foil thickness in transmission electron microscopy (TEM) specimens prepared by electro-polishing, resulting in artificial phase separation like contrast in TEM image. Partially crystallized samples were composed of α-Al nanocrystals with little solute content and an amorphous matrix. No solute enrichment was found at the interface between α-Al and the amorphous matrix, which acts as the heterogeneous nucleation sites for further formation of α-Al crystal, resulting in interconnected nanograin microstructure.

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We examined relaxation and crystallization behavior of the ternary Zr₅₀Cu₄₀Al₁₀ metallic glass by using positron annihilation and transmission electron microscopy (TEM). Observed changes in positron annihilation lifetime of the alloy annealed isothermally at 673 K, which is below the glass transition temperature, correlate well with observed density changes; while coincidence Doppler broadening (CDB) spectra exhibit no significant change. These observations demonstrate that free volume decreases without a rearrangement of atoms during structural relaxation. On the other hand, CDB spectrum has exhibited considerable changes when the same alloy was annealed at 773 K. TEM observations suggested that crystallization occurs via growth of spherulites of several hundred nm in diameter, which themselves are composed of radially grown grains. Chemical analysis revealed that Cu atoms are partitioned out during the growth of the spherulites. Diffraction study indicated that the unit cell of the crystalline phase belong to an orthorhombic system with a=0.892, b=0.550, and c=1.060 nm; while remaining inter-spherulite regions are found to crystallize into an fcc phase with a=1.28 nm, which is probably isostructural to the τ₃ phase.

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In order to investigate the role of Al on the thermal stability of supercooled liquid state, the local structures of Zr₇₀M₃₀ and Zr₇₀M₂₀Al₁₀ (M=Ni, Cu) metallic glasses have been studied by the X-ray diffraction and EXAFS measurements. It is found that the different effect of Al substitution on the local structures around Cu and Ni elements is exhibited. No characteristic change is observed in the local structure in the Zr–Cu metallic glass by Al substitution, whereas a drastic change in the environment around Ni atom can be confirmed in the Zr–Ni metallic glass. That is, the coordination number of Zr around Ni decreases significantly by substitution of Al in the Zr–Ni metallic glass. This would be caused by the preferential correlation between Al and Zr. This result suggests that Al plays a dominant role on the formation of novel local structure with a decomposition of the tetragonal Zr₂Ni-like local environment in the Zr–Ni binary alloy. We conclude that the novel local structure contributes to the stability of the supercooled liquid state in the Zr–Al–Ni metallic glass.

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The electropulsing-induced low temperature crystallization (e-LTC) of marginal amorphous (a-) alloys, a-Cu₅₀Ti₅₀ and a-Pd₈₀Si₂₀, and a bulk amorphous alloy, a-Zr₆₀Cu₃₀Al₁₀, was investigated by electropulsing at room temperature (RT) and in liquid nitrogen (LN₂). Electropulsing was made by means of discharge of a condenser which is characterized by the initial current density, i_d0, and the decay time, τ, where the frequency of the principal constituent Fourier component of the electropulsing is 1⁄2πτ. The range of i_d0 was between 10⁸ and 10¹⁰ A/m² and that of τ was between 0.1 and 20 ms. For all the amorphous alloys, the e-LTC took place during single electropulsing with i_d0 beyond the threshold current density, i_d0,c, where i_d0,c was a function of τ. The maximum specimen temperature during the e-LTC was, e.g., 200 K for electropulsing in LN₂, indicating that the e-LTC is associated with an athermal process, the resonant collective motion of the relatively high density region here. The dependence of i_d0,c on τ found for electropulsing in LN₂ showed good agreement with that observed at RT, indicating that the density fluctuation responsible for the e-LTC was that frozen at the glass transition temperature. The transmission electron microscopy observation revealed that crystallites formed by the e-LTC showed crystallographic alignment with each other, suggesting that the transformation of the relatively high density regions to a crystalline phase took place. The underlying mechanism of the e-LTC was discussed.

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Deformation behavior of a supercooled liquid region in melt-spun Zr₆₀Al₁₅Ni₂₅ and Zr₆₅Al_7.5Cu_27.5 metallic glass was investigated. The viscous flow behavior is very sensitive to the strain rate and the size of crystalline precipitates, which can be classified into 4 types based on shape of the stress–strain curve: stress overshoot mode, stable viscous flow mode with constant flow stress, strain hardening mode and strain softening mode. The strain hardening and strain softening are due to the crystalline phase distribution in supercooled liquid. The strain hardening mode was observed in Zr₆₀Al₁₅Ni₂₅, while Zr₆₅Al_7.5Cu_27.5 deformed with strain softening mode rather than strain hardening mode. Tensile deformation enhanced thermal crystallization in a supercooled liquid region was observed in Zu₆₀Al₁₅Ni₂₅.

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The concepts of melt strength or fragility, borrowed from the description of inorganic and molecular glasses, has become popular also for metallic alloys: the kinetic fragility is described by the viscous behaviour of the liquid and the thermodynamic fragility by the entropy loss on undercooling. Using the data presently available on viscosity and introducing a new index, the reduced span of the glass transition range, it is shown that kinetic data comply reasonably well to the general trend of the strong-fragile classification. On the other hand, there are discrepancies for the thermodynamic fragility of metallic glass formers with respect to conventional ones. A recent report in Nature (Novikov and Sokolov, October 2004) has suggested a correlation between melt strength/fragility and the elastic moduli of the glassy material (namely the ratio of the bulk to shear modulus). This is checked for metallic glasses which were not discussed by the Authors of the Nature paper, next to inorganic and organic glasses. It is shown that considering a larger material basis and extending the number of property values in the data base, the correlation becomes rather poor. There is, however, the possibility of distinguishing among each class of glasses, e.g. inorganic, organic, metal–metal and metal–metalloid.

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A thermodynamic analysis of the Nb–Ni–Ti system has been performed following the CALPHAD technique. To enable the thermodynamic description of the binary systems, the results from a previous evaluation were adopted for the Nb–Ni, Nb–Ti, and Ni–Ti systems. However, a slight modification of the parameters was applied to the bcc and Nb₆Ni₇ phases in the Nb–Ni system, when considering the ternary phase equilibria. The phase boundaries of the Nb–Ni–Ti ternary system at a constant 28 mol%Ni and 60 mol%Ni were determined experimentally by differential scanning calorimetry. A thermodynamic assessment of the ternary system was performed based on the experimental information as well as the reported phase boundaries of the isothermal sections of the Nb–Ni–Ti system at 700, 800, and 900°C. Our calculations reveal that this system includes 15 types of ternary invariant reactions. The ternary eutectic temperature was between 901.6 and 1063.7°C.

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The glass-forming ability of Zr–Ti–Be ternary alloys has been evaluated by coupling the Davies–Uhlmann kinetic formulations with the CALPHAD approach. In the computations, time-temperature-transformation (TTT) curves were obtained, which are a measure of the time necessary for the formation of detectable amounts of a crystalline phase from a supercooled liquid as a function of temperature. The critical cooling rates were calculated from the TTT curves, and these enabled us to evaluate the glass-forming ability of this ternary alloy. The driving force for the crystallization of the crystalline phases was derived from the Gibbs energy functions of each phase, where thermodynamic calculations were carried out using a simple ternary extrapolation of the binary data sets with no solubility of the third element in the binary phases except for the liquid, hcp, and bcc phases. The evaluated glass-forming compositional range was in good agreement with experimental data from the Be-rich side. However, the calculated critical cooling rates for some alloys were too low. The validity of the ideal mixing of the metastable ZrBe(B2) and TiBe(B2) phases, and the possibility of the formation of the ternary B2 phase are also discussed from an ab initio energetic point of view, and the critical cooling rates were recalculated assuming an ideal mixing of the metastable ZrBe(B2) and TiBe(B2) phases. The results show that the magnitude of the calculated values achieved was reasonable.

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The structures and magnetic properties of Pr–Fe–Al alloys produced by the metallic mold casting method were investigated. The Pr–Fe–Al alloy consisted of the amorphous phase together with the non-ferromagnetic Pr phase. Magnetic measurements confirmed that the origin of coercivity in the alloys was the amorphous phase. It was found that the Curie temperature and coercivity of the alloys were strongly dependent on the composition of the amorphous phase.

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The glass-forming ability (GFA), thermal stability and mechanical properties of bulk glassy Pd₇₉Cu_6−xAu_xSi₁₀P₅ (x=0–6 at%) alloys were studied. The results revealed that the minor substitution of Au for Cu strongly affects the thermal stability and GFA of Pd–Cu–Au–Si–P alloys. The alloy in which 2 at% Au was added to substitute Cu (Pd₇₉Cu₄Au₂Si₁₀P₅) exhibits the broadest supercooled liquid region (ΔT_x=80 K) and possesses the highest GFA among the alloys investigated. The critical diameter for glass formation of this alloy reaches ∼7 mm by copper mold casting. The GFA is dramatically reduced when the Au content is more than 5 at%, beyond which no bulk glasses could be formed. The Young’s modulus, yield strength and maximum compressive strength of the best glass former (Pd₇₉Cu₄Au₂Si₁₀P₅) are 87 GPa, 1525 MPa and 1660 MPa, respectively, with a compressive plastic strain over 13%.

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Glass-forming ability and mechanical properties of Fe₄₃Cr₁₆Mo₁₆C₁₅B_10xSm_x alloy were systematically studied in terms of the effect of substitution of rare-earth element Sm for the metalloid element B from 0 to 6 at%. It was found that the thermal stability and glass-forming ability of studied alloys were greatly enhanced by the replacement of B with Sm. With merely 1 at%Sm addition, the supercooled liquid region was extended from 66 to 88 K, and the diameter of the cast rod with fully glassy state increased from 1.5 to 4 mm. When the Sm content is in the range of 2 to 4 at%, the critical diameter for glass formation further increased up to 5 mm. The mechanical properties were also greatly improved by the Sm additions. The Young’s modulus and compressive strength increase respectively from 140 GPa and 2400 MPa for the Fe₄₃Cr₁₆Mo₁₆C₁₅B₁₀ alloy to 189 GPa and 3400 MPa for the Fe₄₃Cr₁₆Mo₁₆C₁₅B₈Sm₂ alloy. However, no improvement in plasticity was observed in the Sm-added glassy alloys. Similar to the Sm-free glassy alloys, the Sm-doped glassy alloys deformed inhomogeneously and failed in a brittle manner. The mechanism for the improved GFA by the addition of Sm is discussed.

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The thermal stability and the mechanical behavior of Zr₆₅Al₁₀Ni₁₀Cu₁₅ and Zr_52.5Al₁₀Ni₁₀Cu₁₅Be_12.5 bulk metallic glasses (BMGs) were investigated by differential scanning calorimetry, uniaxial compressive test, ultrasonic method, and nanoindentation. The substitution of Zr by Be significantly improved the thermal stability of the amorphous phase, exhibited by a wide supercooled liquid region of 116 K. The Be containing BMG exhibited a compressive strength of 1780 MPa, and in particular a high plastic strain of about 6%. The simultaneous operation of multiple shear bands during plastic deformation in Zr_52.5Al₁₀Ni₁₀Cu₁₅Be_12.5 BMG is proved by the less pronounced serrated flow during the loading process in the compression and nanoindentation, as well as the fracture surface morphologies. A high Debye temperature derived from the ultrasonic measurements indicates a condensed atomic arrangement in the Be containing BMG, and may responsible for the high thermal stability.

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The room temperature creep behaviors of Ce-based bulk metallic glasses were examined by the use of nanoindentation. The creep rate and creep rate sensitivity of Ce-based BMGs were derived from indentation creep curves. The low creep rate sensitivity of Ce-based BMGs indicates that the room temperature creep is dominated by localized shear flow. The experimental creep curves can be described by a generalized Kelvin model. Furthermore, the creep retardation spectrum is calculated for the Ce-based metallic glasses. The results showed that creep retardation spectrum consists of two relatively separated peaks with the well defined characteristic relaxation times.

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The preparation of Ti₅₀Cu₂₈Ni₁₅Sn₇ metallic glass composite powders was accomplished by mechanical alloying of pure Ti, Cu, Ni, Sn and WC for 18 ks. In the ball-milled composites, initial WC particles were homogeneously dispersed in the Ti-based alloy glassy matrix. The metallic glass composite powders exhibited a large supercooled liquid region just below the crystallization temperature. The presence of WC nanoparticles did not change the glass formation ability of amorphous Ti₅₀Cu₂₈Ni₁₅Sn₇ powders. The as-milled Ti₅₀Cu₂₈Ni₁₅Sn₇ and composite powders were consolidated by vacuum hot pressing into compact discs with a diameter and thickness of 10 and 4 mm, respectively. Microstructural analysis showed that the bulk metallic glass composite contained submicron WC particles homogeneously embedded in a highly dense nanocrystalline/amorphous matrix. Incorporation of WC into consolidated composite compacts resulted in a significant increase in hardness.

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Effect of Ag additions on the precipitate microstructures of the Al–10Mg alloys has been investigated using transmission electron microscopy (TEM) and electron diffraction.
In the Al–10Mg alloy aged at 240°C, age-hardening response is attributable initially to an array of coarse-scale, sparsely distributed rod-like and/or plate-like β′ precipitate (particles). At the maximum hardness, the microstructure contained an increased volume fraction of coarse-scale β′ and β precipitate particles. In a well over-aged condition, the microstructure exhibited very coarse-scale β precipitate particles. However, in the Al–10Mg–0.5Ag alloy aged at 240°C, fine-scale and uniformly distributed icosahedral quasicrystalline precipitates were observed in the early stages of ageing, and it was to be replaced by the metastable crystalline T phase after the alloy is aged for 2 h at 240°C. The T phase formed as faceted rods parallel to ⟨110⟩_α directions appeared to be the primary strengthening constitute exhibiting maximum hardness. The globular β precipitate particles were observed to be replaced by the metastable rod-like T precipitate particles after the alloy was aged 72 h at 240°C, and the β phase is confirmed to be the equilibrium constitute phase in the over-aged ternary Al–10Mg–0.5Ag alloy.

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In present study, abnormally coarsened grains in high purity aluminum foils with cube texture ({100}⟨001⟩) after a final annealing was investigated using SEM/EBSP method. Most of abnormally coarsened grains had Goss ({110}⟨001⟩) or S ({123}⟨634⟩) orientations. The coarsened grains with Goss and S-orientations were surrounded by Σ5 and Σ7 coincidence boundaries, respectively. This result clarified that these coincidence boundaries would enhance the abnormal grain growth of Goss and S oriented grains. Grain boundary energy of sub-boundaries between cube-oriented grains provided the driving force for the abnormal grain growth. The distribution of Goss oriented grains in the partially annealed foils was characterized by SEM/EBSP method. This characterization revealed that many Goss-oriented grains were distributed in the transition band on the central layer of the sheets.

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Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures of 373 to 673 K by optical and SEM/EBSD metallographic observation. The hot-deformed alloy had fine-grained structures developed by grain fragmentation due to continuous dynamic recrystallization (cDRX). Temperature dependence of the average grain size (D) is categorized into three temperature regions, i.e. (a) an incubation period for grain growth at <450 K, (b) rapid grain coarsening at 473–523 K, and (c) normal grain growth at T>550 K. The number of fine grains per unit area, however, is reduced remarkably even in region (a). These lead to grain coarsening taking place continuously in the whole temperature regions. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with cDRXed grain structures can be mainly controlled by grain coarsening accompanied with no texture change, that is continuous static recrystallization (cSRX).

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It has been found that phase separation, i.e., D0₂₂ precipitation in the supersaturated L1₂ matrix to form the L1₂+D0₂₂ equilibrium state, stagnates in the Ni₃Al_0.52V_0.48 alloy under a certain thermodynamic condition. This stagnation originates from the suppression of the long-range vanadium diffusion in the L1₂ matrix, so-called diffusion blocking. Because diffusion blocking is inherent to the L1₂ structure, its occurrence depends largely on the morphological features of the L1₂ matrix. In this study, the microstructure evolution during the phase separation of the Ni₃Al_0.40V_0.60 alloy was examined from the viewpoint of the relation between the variation in the initial microstructure and the appearance of the effect of diffusion blocking. Our results showed that cuboidal domains of about 30 nm on a side formed in the initial L1₂ matrix and that the D0₂₂ regions appeared at the domain boundaries. The microstructure evolution of the alloy was found to proceed via the rearrangement, combination, and growth of these D0₂₂ regions, accompanying vanadium migration of about 20 nm in the L1₂ matrix. The requisite migration length was determined by the size and density of the initial D0₂₂ regions, which depend on the size of the L1₂ cuboidal domains. A shorter migration length than that in the case of the Ni₃Al_0.52V_0.48 alloy was presumed to be advantageous to concealing the effect of diffusion blocking. On that basis, it was concluded that the occurrence of the phase separation in the Ni₃Al_0.40V_0.60 alloy was attributed to the reduction in the size of the cuboidal domains in the initial L1₂ matrix.

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Casting aluminum alloys are highly heterogeneous materials with different types of voids that govern the mechanical behavior of the material. In this paper, based on the analysis of a cylindrical void model and the assumption of matrix incompressibility, the void evolution of a casting aluminum alloy is derived. Through the analysis of the micro-velocity and the strain fields of the cylindrical void model, an endochronic constitutive equation involving void evolution is obtained for cast aluminum alloys. The corresponding finite element procedure is developed and applied to the analysis of the mechanical behavior and the porosity of casting aluminum alloy A101. The computed results show satisfactory agreement with experimental data.

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We investigated the effect of cold working on the elastic properties of a newly developed multi-functional β titanium alloy, GUM METAL, using in-situ XRD and EBSP analysis. Mechanical and physical properties are changed dramatically by cold working. The alloy has a low elastic modulus (40 GPa), high strength (more than 1100 MPa), high elastic deformability (2.5%) and super-plastic like deformability at room temperature without work hardening. The elastic behavior of the cold worked specimen shows non-linearity, with the gradient of the stress–strain curve in the elastic region continuously decreasing with a stress increase. In-situ XRD measurements during tensile loading show that all β peaks shift monotonically to higher 2θ angles with increasing tensile strain up to 2.7%. This result suggests that the elastic behavior in the alloy is not accompanied by phase transformations, such as stress-induced α″. Additionally, EBSP analysis reveals that the deformation mode in the alloy does not relate to {112}⟨111⟩ or {332}⟨113⟩ twinning. The microstructure of the alloy during deformation is characterized by localized distorted regions ranging in size from several tens of micrometers to submicrometers, with elastic strain located hierarchically in the alloy. It is likely that this microstructure is attributable to its elastic anomaly, which arises at this specific alloy composition of the multifunctional alloy. The above elastic anomaly in the alloy seems to contribute to the development of the unique microstructure during plastic deformation, as well as to its macroscopic elastic behavior.

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The authors found that a liquid Cu droplet wetted and spread very widely on a solid substrate of Fe in a reduced atmosphere after the surface oxidation of the substrate. The mechanism of the unusual wetting behavior was investigated by using surface-oxidized Fe substrate with liquid Cu, Ag, Sn, and In. It was found that under a reduced atmosphere condition, fine pores were formed at the surface of the substrate which had been oxidized, and that the pores were connected to each other continuously over the whole surface. The liquid metals penetrate into these pores by capillary force to cause the unusual wetting behavior.

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We have already developed a novel β-type titanium alloy, Ti–8Fe–8Ta–4Zr, for biomedical applications. Ti–8Fe–8Ta–4Zr showed higher strength than conventional biomedical titanium alloys, such as Ti–6Al–4V ELI, Ti–6Al–7Nb, and Ti–13Nb–13Zr. In addition, the alloy also showed higher corrosion resistance than cp-Ti and Ti–6Al–4V ELI in Hanks’ solution. In particular, the breakdown potential of the alloy (the pitting potential) was over 3.5 V vs. SCE (saturated calomel electrode) and much higher than those of cp-Ti and Ti–6Al–4V ELI. A slightly active region was observed at about 1.7 V vs. SCE that may be related to the high breakdown potential.
In this study, the surface oxide films on Ti–8Fe–8Ta–4Zr after anodic polarization at 1 and 3 V in Hanks’ solution were characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy to elucidate the high corrosion resistance mechanism of the alloy in Hanks’ solution. In addition, the surface oxide film on the alloy before anodic polarization was also characterized for comparison.
The surface oxide film on Ti–8Fe–8Ta–4Zr is grown with anodic polarization. Calcium phosphate is formed on the alloy after polarization. The corrosion resistance of the alloy after polarization at a potential above 1.7 V is improved by the concentration of iron and titanium in the surface oxide film. A titanium hyper-oxidized layer with a low iron concentration is observed within the surface oxide film. This layer is generated with polarization and worked as a corrosion-protective layer. The slight active region on the polarization curve may be caused by the dissolution of iron and titanium.

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Sn–Ag–Cu lead-free solders have recently been applied generally in electrical packaging, but a discoloring of the solders often occurs at the injection-ball or the reflow processes. This study investigates the solidification surface characteristics of both the Sn–3.5Ag alloy and the Sn–3.5Ag–2.0Cu alloy to discuss and clarify the differences in composition between the surface and the thin film of subsurface. The results indicate that the solidification surface films of the Sn–3.5Ag–(2.0Cu) are mostly composed of SnO phase and SnO₂ phase. The concentration of Sn⁴⁺ is higher than that of Sn²⁺ on the film. And the binding energy of O atoms increases at sites near the solidification surface. On the solidification surface thin film, the Ag content of the Sn–3.5Ag–2.0Cu specimen is higher than the Sn–3.5Ag specimen. In addition, there is few Cu on the solidification surface film of the Sn–3.5Ag–2.0Cu specimen, and adding Cu into Sn–3.5Ag alloy not only can repress the growth of the SnO_x phase but also reducing the degree of discoloring.

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Aluminum has excellent workability and surface finishing, but it corrodes easily and has low hardness. Therefore, in this study, an excellent high corrosion resistance oxide film was prepared by hydrothermal treatment on aluminum in the primary treatment. In the secondary treatment, MnO₂ was immobilized on high corrosion resistance oxide film by hydrothermal treatment.
Aluminum was treated by hydrothermal treatment for 30 min under 483 K (2.0 MPa) conditions in a 0.04 kmol/m³ aluminum nitrate aqueous solution. Adding aluminum nitrate to prepared thick boehmite film (20 μm) by formed globules in the primary treatment, and it possessed a wide surface area. The primary processing film was treated for 30 min under 453–483 K (1.0–2.0 MPa) conditions in a potassium permanganate aqueous solution by hydrothermal treatment, and nanoorder MnO₂ (30 nm) was immobilized onto the boehmite film. MnO₂-boehmite film with wide surface area and high oxidation activity was prepared.

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As a fundamental study to develop a new process for treating iron-lead base alloys, “speiss”, with a considerably high content of arsenic or antimony, which are produced in smelting lead ores or secondary materials of lead under a strongly reductive condition, the phase relations and the minor elements distribution of copper, silver, gold and platinum in the Fe–Pb–As and Fe–Pb–Sb systems saturated with carbon were determined at 1473 K by a quenching method. It was found that a miscibility gap composed of an iron-rich alloy phase with a very small content of lead and a lead-rich alloy phase with very few contents of iron and carbon extended over the wide concentration range. Arsenic was mostly distributed in the iron-rich alloy phase, while antimony almost evenly in both phases. For the distribution of precious metals, it was found that silver was mostly enriched in the lead-rich alloy phase, platinum in the iron-rich alloy phase, while gold and copper almost evenly in both phases. Based on the obtained data of the phase separation and using thermodynamic data for the Pb–As and Pb–Sb binary systems, the activity coefficients of arsenic and antimony in the Fe–As and Fe–Sb systems saturated with carbon at 1473 K were derived and expressed by a formula with the interaction parameters.

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There is a concept that the surface roughness is the structure-type of the optical gradient function because the material volume fraction gradually changes along the surface normal from the vacuum (or air) to the material. In this sense, the controlling the surface undulations corresponds to the controlling the gradient-profile.
Sputtered Al film, AlN film, and incompletely-nitrided Al film (Al–N film) has been investigated from the view point of forming the mesoscopic scaled surface roughness because it can be applied to, e.g., the solar absorption coating, the solar cell and/or the diffusive coloring. The surface structures have been characterized and the growth condition dependence, such as the degree of nitriding which is controlled by changing mixing ratio of N₂ and Ar sputtering gases, the film thickness (d_f), and the substrate temperature (T_sub), are systematically investigated. The following controllable factors about surface structure are confirmed. The characteristic of the form of protuberances on the surface depends on the degree of nitriding. The height and the width of the protuberances can be controlled by d_f and/or T_sub.

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Si-based nanoparticles, nanochains and nanowires were synthesized by smelting reduction method which includes a high temperature carbothermic reduction of silica-rich melt to SiO vapor and transfer of the vapor with Ar carrier-gas to cooler surfaces inside the experimental reactor where the nanoparticulates were deposited. Features of the process have been discussed in our previous paper. In this paper, the synthesized nanoparticulates were characterized by using XRD, XPS, EDX, TEM and HRTEM analysis. The deposition temperature was found to be the crucial parameter governing the nanoparticulate morphology and phase composition. The nanowires were obtained in the high temperature range of 1320–1570 K. It is found that the as-obtained nanowires were composed of a SiC core and an amorphous sheath of silicon suboxide. The nanowires had diameter ranging from 20 to 60 nm and length up to several microns. The rounded nanoparticles of 30–50 nm in diameter were deposited at locations under temperatures lower than 920 K. They were mainly composed of amorphous silicon suboxide which could be decomposed under certain conditions yielding Si nanocrystallites embedded into the oxygen enriched suboxide matrix. The nanocrystallite size was estimated to be of 3–8 nm although much larger, up to 50 nm, Si crystals were detected at high temperature locations.

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In this study, 5052 Al–Mg alloy was pre-treated and friction stir processing (FSP) was then performed on the specimens to explore the deformation resistance. The experimental results indicate that the FSP specimens not only had better tensile properties but also better vibration fracture resistance. It is significant that the tensile elongation and deformation resistance tended to increase as the grain was refined by friction stir processing. Results show that the use of FSP yielded uniform hardness distribution and slightly larger n values which improved the vibration fracture resistance of the specimens. However, even without FSP, more uniform elongation and larger n values could still improve the vibration fracture resistance of the specimens. Consequently, the uniform elongation and larger n values play an important role in increasing vibration fracture resistance. As for crack propagation, the FSP specimens revealed only a few slip bands in the vicinity of the main crack, and the 5052H34 specimen displayed a few slip bands in the vicinity of the main crack. However, more slip bands were observed in the vicinity of the main crack on the 5052-O specimens, and there were deformation traces and advancing cracks rising at the front of the main crack. Consequently, vibration fracture resistance can also be better improved if the crack initiation and propagation through the stir zone of FSP specimens are controlled. This is correlated with the formation of fine grains through dynamic recrystallization in the vicinity of stir zone.

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Magnetic domain structures in Fe_73.5Si_13.5B₉Nb₃Cu₁ alloys annealed at different temperatures have been observed in situ under external magnetic fields by electron holography. Under a weak magnetic field of less than several A/m, a typical magnetization process of the high permeability material is observed in the specimen annealed at 823 K consisting of the bcc Fe–Si nanocrystalline and the amorphous matrix phase. On the other hand, in the specimen annealed at 973 K consisting of large Fe–Si grains and Fe–B compounds, many domain walls are observed at the boundaries between Fe–Si grains and also between Fe–B grains. Under a strong magnetic field of more than several kA/m, domain walls are observed only between Fe–B grains. The result indicates that the boundaries between Fe–B grains act as stronger pinning sites of domain walls than the boundaries between Fe–Si grains and those between Fe–Si and Fe–B grains in the Fe_73.5Si_13.5B₉Nb₃Cu₁ alloy annealed at 973 K.

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Influences of composition on magenetostriction of Fe–Sm alloy thin films prepared by D.C. magnetron sputtering process were investigated. Composition of formed film was ranged from 24 to 59 at%Sm. Negative, that is, compressive magnetostriction was observed of Fe–Sm thin films. The magenetostriction of thin films was varied with composition rate of Fe–Sm alloy. The giant magnetostriction (GM) over 1000 ppm at 1200 kA/m was observed from 24 to 34 at%Sm for Fe–Sm amorphous film. The limited value of GM at 1200 kA/m was 1280 ppm of Fe–29.3 at%Sm alloy film.

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Closed recycling process for low-grade scrap of Al-based composite materials was developed. Flux treatment with water-soluble halide is a key technique in this process. In the present work, flux treatment conditions were discussed from the viewpoints of separation and recovery of base material, reinforcement and flux. Optimum separation condition was obtained for the NaCl–KCl–KF flux treatment. The recovered aluminum alloy can be recycled for various usages. The recovered SiC particles cannot be reused as reinforcement because of the coexistence of contamination, therefore it is necessary to eliminate these contaminates or to find the other uses. The recovered flux is reusable with supplemental addition of fluoride.

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The viscoplastic properties of the Sn-rich phase and Sn–Ag–Cu eutectic constituent in a Sn–3.5Ag–0.75Cu lead-free solder were determined by performing microindentation tests on these individual phases. Material parameters in Norton’s law for each phase were successfully identified by fitting the experimentally obtained rate-dependent indentation load (P) vs penetration-depth (h) curves, as well as indentation-creep data, with the corresponding Finite Element (FE) simulation results. For this material parameter identification, an appropriate indenter-penetration depth for a given size of a phase, where the P–h response is not affected by the other neighboring phases, was determined by FE simulation.

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The surface deformation features in ultrafine-grained copper produced by equal channel angular (ECA) pressing, which was cyclically deformed at temperatures between room temperature and 573 K under a constant stress amplitude of 200 MPa, were investigated. It was found that the surface deformation features and damage behaviour are strongly dependent upon the testing temperature. For examples, large-scale shear bands (SBs) formed at room temperature, whereas finer and discontinuous SBs, instead of large-scale SBs, were found to become the dominant feature with increasing temperature (below recrystallization), resulting from the reduction in quantity and volume fraction of grain boundaries as a consequence of grain growth and the enhanced dislocation slip. When the temperature is above recrystallization, no clear SBs were observed and dislocation slip deformation within grains governed the plastic deformation of UFG copper, causing nucleation of cracks along slip bands in grains or along grain boundaries, in contrast to the nucleation along SBs at temperatures below recrystallization.

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High-strength Mg–Y–Zn alloy plate was obtained by friction stir processing (FSP) after casting. In this study, the Mg–Y–Zn alloy by FSP showed sufficiently high performance with low cost. As-cast material was held at 723 K for 95 h. It then showed a lamellar structure, which might have resulted from long-range periodic structure. However, this lamellar structure showed very low hardness, as did the as-cast material. Plates cut from heat-treated ingot were processed as single, overlapped double, and multiple pass FSP. After FSP, each processed materials was cut for microscopic measurement and hardness testing. Ultra-fine-grained microstructures are obtainable using the FSP. Micro-Vickers hardness tests for each pass result in the occurrence of strengthening for FSP of Mg–Y–Zn alloy. There was little change in grain size and hardness of pre-stirred zone by the next pass of stirring.

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Full three-dimensional finite volume method (FVM) simulation was carried out for two types of Mg alloys. The load-stroke curve, effective strain, effective stress, and strain rate were obtained during the virtual superplastic forging process. The above results for fine-grained Mg alloy showed localized flow behavior because of the change in dominant deformation mechanism at a high strain rate above ca. 0.8 s⁻¹. However, RS P/M Mg–Zn–Y alloy showed relatively uniform metal flow at the same strain rate.

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A non-destructive magnetic Barkhausen emission (MBE) technique was applied to assess thermal degradation of 2.25Cr–1Mo steel, exposed to 630°C for up to 4800 h. The peak position and the peak amplitude in MBE profile decreased and increased, respectively, as a linear function of cube root of isothermal degradation time. These changes in MBE profile were related to the carbides coarsening during thermal exposure. An empirical correlation between the ultimate tensile strength (UTS) and the peak position in the MBE profile was also obtained by a linear regression analysis.

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