As a new type of material, the nanocrystalline material has drawn world-wide attention in recent years. As a challenge subject, much work has been done concerning the grain size dependence of mechanical properties, e.g., on the Hall-Petch relationship of these new materials. The currently-known Hall-Petch relations in the nanocrystalline material were examined in this work with an emphasis on crystallized nanocrystalline materials. Nanocrystalline materials usually show decreased microhardness compared with the prediction from the Hall-Petch relationship and even a negative Hall-Petch slope. The possible mechanisms for above phenomena were analyzed in relation to the quantitative measurements on the microstructures of crystallized nanocrystalline materials by means of positron annihilation spectroscopy and X-ray diffraction.

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The replacement of Cu by 10 at%Pd for an amorphous Zr₆₀Cu₃₀Al₁₀ alloy was found to change the crystallization process from the single stage of amorphous (Am)→Zr₂Cu+Zr₂Al to the two stages of Am→Am′+Zr₂(Cu, Pd)→Zr₂(Cu, Pd)+Zr₃(Al, Pd)₂ in the maintenance of the wide supercooled liquid region before crystallization. After the melt-spun amorphous alloys were annealed for 1.2 ks at 726 K and the volume fraction (V_f) of compound reached as large as 75%, the particle size and interparticle spacing of the compound particles in the amorphous matrix were 10 and 1.5 nm, respectively. The residual amorphous phase enabled the maintenance of the nanoscale compound particles. The nanoscale mixed phase alloy remains good bending ductility even at V_f=75% and exhibits high tensile strength (σ_f) of 1910 MPa which is higher than that (1640 MPa) for the amorphous single phase. The increase of the thermal stability of the remaining amorphous phase is presumably due to the generation of the strong bonding pair mainly among Zr, Pd and Al. The good ductility of the mixed phase alloy is due to the suppression of embrittlement for the remaining amorphous phase because the partial crystallization is made in the supercooled liquid region. The first achievement of high σ_f and good ductility for the mixed phase alloy with nanoscale Zr₂(Cu, Pd) phase surrounded by the amorphous phase is important for future progress of high-strength nanocrystalline bulk alloys.

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TiAl-0.1–3.0 mol%Be alloys made by the argon arc melting method were investigated to characterize microstructures in cast and annealed conditions using optical microscopy, SEM, EPMA and X-ray diffractometer. The addition of Be to TiAl resulted in a decrease of α₂ phase, thereby coarsening grains and a shift of γ⁄(γ+α₂) phase boundary to Ti-rich side. Two types of Be compound were observed: one was a few micron size of particles which contain a large amount of oxygen and the other was a coarse and eutectic-like phase (θ) which has an atomic ratio of Ti:Al:Be=41:30:29. The solubility limit of Be in TiAl was less than 0.1 mol%. In the (γ+θ) two phase and (γ+α₂+θ) three phase regions, an increase of Be addition beyond the solubility limit resulted in a small increase of Ti/Al compositional ratio in γ phase. A volume fraction of lamellar structure in TiAl–Be ternary alloys was smaller in the cast structure but was larger in the annealed structure than that in TiAl binary alloys which have nearly the same Ti/Al ratio as that in the ternary alloys, because the Be addition may increase the stacking fault energy and will stabilize the lamellar twin boundaries, respectively.

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A Ti-51 at%Ni alloy including aligned particles of Ti₃Ni₄ precipitate formed by aging under an applied stress exhibits an anomalous transformation, i.e., stress induced R(martensite)→B2(parent) transformation. Confirmation of this transformation was made by tensile tests combined with simultaneous resistance measurements. This alloy also exhibits pseudoelasticity associated with twinning when tensile test is made at a temperature sufficiently below its transformation temperature, i.e., in the R-phase state. The stress induced R→B2 transformation and the pseudoelasticity in the R-phase state are due to the internal stress field formed by the aligned particles of Ti₃Ni₄.

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Phase relation of the Zn–Sn system at various pressure up to 7 GPa is investigated by means of isobaric measurement of electrical resistance. Pressure vs. temperature phase diagrams of Zn-91 mol%Sn, Zn-49 mol%Zn and Zn-10 mol%Sn alloys as well as an isobaric phase diagram of the Zn–Sn system at 5 GPa are constructed on the basis of the results. A new eutectoid horizontal caused by the appearance of the high pressure γ phase of tin appears in the phase diagrams. The cross point of the eutectic and eutectoid phase boundaries is 3.9 GPa and 273°C.
An intermediate electron phase with simple hexagonal structure known in many binary alloy systems was not stable in the Zn–Sn system within the present conditions of high pressure and temperature.
In the heating run of temperature vs. electrical resistance curves on the Zn–Sn alloys, a delay of the ending temperature of the reaction at liquidus is observed under high pressures. It is considered to be caused by insufficient interdiffusion of zinc and tin in the liquid phase.

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Deformation and microstructure were investigated on Ti-14 mass%Mo alloy in over aged state using the duplex aging method. In the over aged state only hardness decreased in spite of no change in both size and composition of ω phase. Though the ω phase aged at 623 K for 1×10⁶ s had the maximum hardness and resulted in the brittle fracture through ω→β″ transformation, they became soft by over aging and transformed to α phase within the deformation band. The α particles in the band were sheared by {10\bar11}_α twinning which direction was perpendicular to the band product. The twinning of α particles was regarded as a complementary deformation with volume change in the ω→α transformation. It was suggested that the occurrence of the band product consisted of β+α phases would not be directly connected with brittle fracture.

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Through in-situ TEM observation on an Fe-30.3 mass%Mn-6.1 mass%Si shape memory alloy under extending at room temperature, it is found that on a lower applied stress level, the ε-martensite plates are preferentially formed at interfaces of pre-existing overlapped stacking faults or ε-martensites with γ-phase especially at those near by the stress-concentrated locations e.g. inclusions. It is also observed that the ε-martensite is growing by the motion of partial dislocations resulting in the widening and thickening of stacking faults until it is stopped by another martensite plate or grain boundary. On higher stress level, groups of highly oriented ε-martensite plates are formed by an autocatalytic activating mechanism suggested by the present authors.

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In-situ TEM observation of the deformed specimen on heating from R.T. up to 873 K in an Fe-30.3 mass%Mn-6.1 mass%Si shape memory alloy has been performed. It is found that the thicker ε-martensite plates will be disintegrated layer by layer through the reverse motion and annihilation of partial dislocations and the last induced ε-martensite will be the first to disappear. The in-situ observations on heating of the secondary deformed specimen after once thermo-mechanical cycling has also been conducted, from which the improvement mechanism of thermo-mechanical training can be well explained.

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Anion-exchange separation in chloride media is applied for the preparation of high purity copper. Oxygen free copper (OFC) which has a residual resistivity ratio of 190 is used as a starting material. Copper refined by the purification process based on the anion-exchange separation shows residual resistivity ratio of 2300 which is much larger than that of the starting material. Glow discharge mass spectrometry analysis shows that almost all impurities are effectively removed by the purification process. High purity copper is successfully obtained by the purification process based on the anion exchange separation.

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AC impedance method has been applied to evaluate the performance of Zn, Zn-5%Al and Zn-55%Al coated steels under wet-dry cycles. The wet-dry cycles were carried out by exposure to the alternate conditions of 1 h-immersion in a 0.5 or a 0.05 kmol/m³ NaCl solution and drying for various times at 298 K and 60%RH. The impedances at two frequency points, a high frequency (10 kHz) and a low frequency (10 mHz), were monitored during the cyclic wet-dry exposure. The reciprocals of the high frequency and low frequency impedances were taken as the solution conductance of water layer on the coating surface and the corrosion rate of the coated steels, respectively. The impedance monitoring results showed that the Zn-55%Al coating exhibited the most excellent corrosion resistance under the given conditions. This is attributed to the formation of aluminum oxide on the specimen surface. On the other hand, the corrosion resistances of Zn coated and Zn-5%Al coated steels were almost the same under relatively wet and highly chloride-concentrated conditions. An increase in the chloride concentration of the test solution employed during the wet-dry cyclic test decreased the average corrosion rate in all cases. The average corrosion rate of the Zn-55%Al coating under wet-dry cyclic condition in 0.5 kmol/m³ NaCl solution was lower than that in 0.05 kmol/m³ NaCl by one order of magnitude. The combined wet-dry cyclic exposure test and AC impedance corrosion monitoring is very useful for the mechanistic study of the corrosion of coated steels, as well as the evaluation of their corrosion performance, in marine atmospheric environments.

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By the addition of some definite transition metals Ni, Cr and Zr to the Si–Al–Fe system, the maximum Si content for formation of an amorphous single phase was extended to 50 and 55 at% Si. The Si-based amorphous alloys are characterized by high values of electrical resistivity (11.7–12.3 μΩm) and hardness (∼930 HV). Their crystallization temperatures exceed 700 K, which is higher by about 100 K than those for Si₄₅Al–Fe–Cr and Si₄₅Al–Fe–Ni quaternary alloys. During heat treatment of an amorphous Si₅₅Al₂₀Fe₁₀Ni₅Cr₅Zr₅ alloy at the temperature above the crystallization temperature, a 6-component Si₁₀Al₄Fe₂NiCrZr phase with a tetragonal structure having lattice parameters a=0.6890 nm and c=0.9402 nm is formed as a main constituent phase. The difficulty of the precipitation of the multicomponent crystalline phase with the large volume of unit cell during rapid solidification is presumed to be the main reason for the formation of the Si-based amorphous phase.

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Mechanical alloying through the ball-milling of elemental powders to form the zinc-rich ζ binary Fe–Zn alloy, and the ternaries consisting of 0.12 mass%Si, 1.2 mass%Si, and 2.4 mass%Si, based on the same Fe/Zn ratio was performed. These materials have been designated as ζ, ζ+0.12 mass%Si, ζ+1.2 mass%Si, and ζ+2.4 mass%Si and mechanically alloyed to form their metastable states, η-Zn, FeSi and ζ phases. Differential scanning calorimetry (DSC) measurements of the materials show the presence of characteristic exothermic and endothermic reactions during their continuous transformation to stable equilibrium states. In the ζ+0.12 mass%Si material composition (i.e., Sandelin region), we observe an invariant reaction peak at around 422°C, corresponding to both the eutectic reaction in the Zn–Si and the melting of Zn in the Fe–Zn systems. The observation of the FeSi phase for all the compositions, while absent in coatings of Si bearing steels suggests a relationship between the Sandelin effect and its formation.

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Magnetic properties and phase composition of Nd_4.5Fe₇₇B_18.5 exchange-coupled nanocrystalline composite magnet have been investigated as a function of heat treatment by means of differential thermal analysis, magnetization, X-ray diffraction, and ⁵⁷Fe Mössbauer measurements. Cr content dependence of magnetic properties and phase composition of Cr-added Nd_4.5(Fe_1−xCr_x)₇₇B_18.5 has also been investigated. By annealing up to 853 K, Nd_4.5Fe₇₇B_18.5 amorphous ribbon crystallizes in both t-Fe₃B and Nd₂Fe₂₃B₃. These two compounds are soft magnets and the specimen does not have coercivity. Hard magnetic Nd₂Fe₁₄B is precipitated by annealing up to 943 K, and the specimen becomes hard magnetic. Nd_4.5Fe₇₇B_18.5 nanocrystalline composite magnet annealed up to 943 K consists of 10 mole% Nd₂Fe₁₄B and 90 mol% t-Fe₃B, and the small amount of hard magnetic phase results in large coercivity of this material. With increasing Cr content, coercivity of Nd_4.5(Fe_1−xCr_x)₇₇B_18.5 optimally heat-treated ribbon increases, but remanence decreases. In all the specimens, hard magnet Nd₂Fe₁₄B is formed and the amount is found to decrease with increasing Cr content. This is one of the reasons for the reduction of remanence. Soft magnetic phases which crystallize in the specimen changes from t-Fe₃B to Fe₂B and α-Fe depending on Cr content. Hyperfine magnetic field of Fe–B compound decreases as a function of Cr content, while those of Nd₂Fe₁₄B and α-Fe are independent of Cr content. Therefore, Cr atoms mainly exist in Fe–B compound, not in Nd₂Fe₁₄B and α-Fe, and reduce the magnetization and Curie temperature of soft magnetic phases. In addition, the total amount of soft magnetic compounds decreases by the Cr-substitution for Fe. These influences of Cr atoms result in the decrease of the remanence of this material.

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Millimeter-sized Al–Cu–Ru single quasicrystals in a shape of a pentagonal dodecahedron were produced by slow cooling from just above the melting point. The alloy ingot was held at 1323 K for 2 h. Then it was slowly cooled to 1123 K in 33.3 h and subsequently cooled to room temperature in a furnace. Single quasicrystals were obtained in three compositions, Al_61.6Cu_24.8Ru_13.6, Al_68.1Cu_16.1Ru_15.8 and Al_58.3Cu_27.9Ru_13.8. The compositions of three single quasicrystals fall nearly on a e⁄a=1.75 straight line. An X-ray Laue pattern corresponding to the five-fold symmetry shows a clear petal-like pattern. The X-ray diffraction profiles were measured using a four-circle diffractometer for the Al–Cu–Ru alloys. There is no qualitative difference between Al_61.6Cu_24.8Ru_13.6 and Al_68.1Cu_16.1Ru_15.8.

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