Small dispersed clusters of foreign atoms or a foreign structure in the mother phase, appearing as a precursor or a remnant of phase transformation, are treated by a statistical thermodynamic calculation. The entropy of mixing of the clusters and unclustered atoms is formulated and combined with the enthalpy change associated with the cluster formation to find the equilibrium or quasi-equilibrium state of the dispersion of small particles. It is applied to the cases of the medium range order structure in amorphous alloys, the precursory premartensitic structure, the early stage of aging and precipitation in alloys, etc. It is concluded that the entropy of mixing of small atomic clusters in the matrix plays an important role in the appearance of very fine dispersed structure prior to and/or after various types of phase transformations of metals and other solid materials.

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The hydrostatic pressure is one of the important state variables in phase equilibrium, and its generation techniques have been so much developed that it is now possible to study in detail the effect of pressure on phase transformations. In this overview, the effects of pressure on phase transformations, especially on martensitic transformations, are described in detail, centering around our recent systematic work, since there are still a small number of work in this research field. The effect of hydrostatic pressure on martensitic transformation is fundamentally brought about through an interaction of the hydrostatic pressure with the volume change, expansion or contraction, accompanying the transformations. The volume change is affected by the invar effect in ferrous invar alloys. Therefore, the hydrostatic pressure effect on martensitic transformations may be varied with the type of the martensitic transformations, thermoelastic or non-thermoelastic, athermal or isothermal, and it also depends on the kind of alloys, invar or non-invar. From this point of view, the hydrostatic pressure effects have been examined for those various types of martensitic transformations in various kinds of alloys, which include Fe–Ni, Fe–Ni–C, Cu–Al–Ni, disordered and ordered Fe–Pt, aged Ti–Ni, ausaged Fe–Ni–Co–Ti and Fe–Ni–Mn alloys. It is clearly shown that the martensitic transformation start temperature, M_s, is decreased or increased with increasing hydrostatic pressure, depending on whether the volume change is expansion or contraction. These changes in M_s are in good agreement with theoretical calculations in which hydrostatic pressure dependences of volume change and invar effect are both taken into consideration, using an equation derived by modifying that of Patel and Cohen. Despite those changes in M_s, martensite morphology is not varied with the hydrostatic pressure, irrespective of the type of martensitic transformations and the kind of alloys.

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High-cycle fatigue (HCF) properties of a number of different grades of austempered ductile irons (ADIs) were investigated. Ductile irons were prepared as Y-block castings with three section sizes (25, 50, and 100 mm in thickness). Fatigue specimens were selected from various locations within the castings, austenitized at 1173 K, and then austempered at 573 and 633 K, respectively. HCF tests were conducted by rotary bending method to generate the S–N curves and the associated fatigue limits. As section size increased, the HCF strength of ADI was decreased and affected by the inferior graphite nodule morphology and microshrinkage porosity resulting from the slower solidification rate. The effects of section size, location within the heavy-section casting, and austempering temperatures on the HCF strength of ADI are interpreted in terms of the graphite nodule morphology and microshrinkage pores. An empirical equation was introduced to correlate the fatigue limit of ADI with the impact toughness value and mean nodule diameter.

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The relationship between low-cycle fatigue (LCF) strength of austempered ductile iron (ADI) and cast section size and location was investigated. Uniaxial LCF tests under strain-control were conducted on a number of different grades of ADIs. These ADIs were selected from four positions in Y-block castings with three section sizes (25, 50, and 100 mm in thickness). LCF specimens were cut from specific locations within the castings, austenitized at 1173 K, and then austempered at 573 and 633 K, respectively. Results indicated that LCF strength of ADI degraded with increasing section size due to deteriorated graphite nodule morphology and presence of more microshrinkage pores as a result of the slower solidification rate. The effects of section size, location within the heavy-section casting, and austempering temperatures on the LCF strength of ADI are discussed in terms of the graphite nodule morphology and microshrinkage pores. Fractography with scanning electron microscopy (SEM) was applied to determine the LCF failure mechanisms and fatigue crack propagation modes.

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This study describes a few observations pertaining to the effects produced through the addition of silicon on the tensile and compressive properties and sliding wear response of a zinc-aluminium alloy. The influence of test temperature on the tensile (strength and elongation) properties and sliding speed and pressure on the sliding wear behaviour of the alloys has also been examined. The nature of different microconstituents of the alloys has been taken as a base to explain the characteristics of the specimens.
The study shows that addition of silicon to the alloy system becomes beneficial under test conditions involving higher operating temperatures while the trend reverses at low temperatures. The former has been attributed to the thermal stability attributed by the element at elevated temperatures. On the contrary, the predominating microcracking tendency introduced in the alloy system by the element (silicon) leads to inferior properties under low temperature conditions. Moreover, the lubricating and load bearing capabilities of phases like α and η become effective towards improving the response of the silicon-free alloy under low temperature conditions only and their positive effects cannot be realized at high temperatures in view of (their) low melting points. Thus, addition of silicon becomes helpful under specific conditions only.

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Phase equilibrium between copper matte and SiO₂–CaO–FeO_x–MgO slag with Q=0.35 (Q=mass%CaO/(mass%CaO+mass%SiO₂)) was investigated at 1573 K under the SO₂ partial pressures of 10.1, 50.7 and 101.3 kPa as a fundamental study for thermodynamically discussing oxygen-smelting processes to produce copper. The copper and sulfur solubilities in the slag were found to be independent of p_SO2 when the matte grade was specified, and it was considered that this behavior was ascribed to the constancy of (p_O2⁄p_S2) against p_SO2 at a given matte grade. When the distribution ratio of a minor element, X, between the slag and matte phases was defined as L_x^s/m=(mass%X in slag)/{mass%X in matte}, L_x^s/m for As, Sb and Bi at a given matte grade increased with increasing p_SO2. This behavior was explained reasonably by assuming a mutual reaction between a metallic species in the matte and an oxidic species in the slag. The distribution ratio, L_Ag^s/m, at a given matte grade was almost constant against p_SO2. This was considered to be ascribed to the sulfidic species of AgS_0.5 prevailing in the matte phase and the constancy of (p_O2⁄p_S2) against p_SO2.

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To evaluate the purity of high-purity copper with high accuracy by the residual resistivity ratio (RRR), the optimum annealing condition before the RRR measurement and the diameter dependence (size effect) of RRR for high-purity copper (5N and 6N grade copper) wires, 0.2–2 mm in diameter, annealed under the optimum condition have been investigated.
The most suitable annealing temperature and period were determined to be 923 K and more than 14.4 ks (4 h), respectively. For the size effect on RRR, the relationship between RRR_W (RRR measured for a copper wire with diameter d), RRR_B (RRR of the bulk copper) and the specimen diameter d (mm) was found as follows:
RRR_W⁻¹=RRR_B⁻¹+(3.8×10⁻⁵)·d⁻¹
The product of ρ·λ=6.5×10⁻¹⁶ Ωm² for copper was also obtained from the slope of the above equation. Furthermore, it became clear that the difference in RRR_W is dependent on the specimen diameter and increases with purity of the specimen. Therefore, the influence of the size dependence on RRR must be considered carefully whenever to evaluate and to compare the purity of high-purity metals by RRR.

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In order to clarify the reason for the excellent corrosion resistance of zinc-plated steel coated with magnesium which was electrodeposited from a molten salt, corrosion products in a 5 mass%NaCl aqueous solution were investigated by X-ray diffraction analysis and EPMA. It was found that thin MgO layer was rapidly formed on the surface and acted as a protective film. It was also found that thin MgO layers were formed along the cracks in the zinc-plated layer, and stopped up the cracks and prevented corrosion from proceeding through the cracks. The latter fact means that the magnesium-containing zinc-plated layer has a self-healing ability.

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A new method has been developed to simulate Si K_β X-ray fluorescence spectra of SiO₂–Na₂O binary slags using the DV-Xα molecular orbital calculation. The composition of the slag has been incorporated for the first time in the calculation of the Si_3p partial densitiy of states (PDOS). The calculated Si_3p PDOS dealing with the Na₂O content agreed well with the experimental Si K_β X-ray fluorescence spectra of the 50 mol%SiO₂-50 mol%Na₂O and 33.3 mol%SiO₂-66.7 mol%Na₂O binary slags. The present method was found to provide a very useful means of clarifying the change in shape of the X-ray fluorescence spectrum of the slag with the metal oxide content, and also of understanding the concept of basicity at the same time.

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The electroplating of bright nickel from Watts bath with stepwise additives of gelatin, benzene sulphonic acid and its sodium salt was investigated. Electroplating of fine dispersed nickel layer from the same bath with inclusions of gelatin, benzene sulphinic acid sodium salt, Al₂(SO₄)₃ and SiO₂ was also examined. The effects of bath constituents on the cathodic polarization and the interfacial impedance response during deposition of both forms of nickel was discussed. The surface morphology of the deposits was examined by scanning electron microscopy (SEM) and the crystal structure was elucidated by X-ray diffraction.

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In order to investigate the inhomogeneous current distribution in the silver sheathed Bi2223 tapes, a scanning Hall probe measurement was carried out. The z component of self magnetic field was converted to the local current density, of which spatial change comprised two characteristic features. The inhomogeneity of longitudinal current distribution along the current flow was suggested to be attributed to the positional change of oxide layer thickness due to the work instability. Transverse current distribution is caused from the degree of misalignment of Bi2223 layered grains as well as the distribution of non-superconducting phases.

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