Self-consistent Hartree-Fock-Slater molecular cluster models for iron martensite are presented. The discrete variational method with numerical basis functions is applied to molecular orbital calculations for several clusters of iron martensite. One-electron orbital energies, orbital and overlap populations are utilized to clarify the covalent bonding and charge transfer between carbon and iron atoms. Local density-of-states diagram shows that the band width of the Fe₆ cluster is somewhat narrower than that from the band structure calculation for iron crystal. From the population analysis, it is found that electrons transfer from the first neighbor iron to carbon atom. The number of 3d electrons of the first neighbor iron atoms is increased by bonding interactions with carbon atom. The character of interactions among C 2s, 2p and 4s, 4p and core orbitals of the first neighbor iron are of rather strong antibonding. Qualitative explanation for observed magnetic fields at iron nuclei around the carbon atom is also given.

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Effects of the brittle zones with multiple crackings on deformation and fracture behaviour of ductile fibre-composites were investigated by using composites consisting of two components of aluminium-alumina as well as three components of stainless steel-brittle zone-aluminium. The strength of the fibres was raised as long as the brittle zone with multiple crackings adhered to the fibres and was not fractured in the transverse direction by the compressive stress, as ascertained in our previous work. The effects of grain size of ductile aluminium fibre on deformation behaviour of the binary aluminium-alumina composite were discussed by using the strengthening mechanism of the brittle zone previously proposed by us. The strengthening effect of the brittle zone on the ternary composite arose only from the mechanical interaction between the brittle zone and the fibre. The mechanical interaction between the brittle zone and the matrix was negligible since the interfacial bond between them was very weak. The brittle zone in itself did not affect fracture behaviour due to spalling or fracture by the compressive transverse stress prior to composites fracture. The weak bond between the brittle zone and the matrix caused bridging or splitting.

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The aging process in a Cu-4%Ti alloy at 300–600°C has been studied by means of X-ray small-angle scattering (SAS) and X-ray powder diffraction. Analysis of SAS data showed that the aging process is subdivided into four stages I–IV. Integrated intensity Q₀ and Guinier’s radius of gyration increased with aging time for the stages I and II. The rates of increase during the stage II were larger than those during the stage I. Q₀ remained constant for the stage III, but it decreased with aging time for the stage IV. At temperatures above 450°C the aging process began from the stage II, while below 400°C the stages I–IV proceeded in sequence. During the stage I the main diffraction lines did not move, but during the stage II they moved to a high angle side with aging time. In the stage III, they coincided with diffraction lines of a α₂-phase. It is concluded that zone-complexes grow encroaching on the matrix during the stage I, while the inner-zone of zone-complexes grows through the decrease of solute concentration of the matrix during the stage II. The cause of the difference in the aging behavior with temperatures is related to the dependence of the interdiffusion coefficient on temperature.

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Structural changes taking place in the precipitation–hardened Al–Zn alloys studied through various techniques are reviewed. Further, results of the experiments carried out in the present work on some Al–Zn (4 to 35 at%) alloys using several techniques like electrical resistivity, X-ray diffraction and transmission electron microscopy (TEM) have been mentioned. Based on these results, the structural changes taking place in this system are discussed in the light of the two metastable solvus curves.

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A process to prepare high purity iron with good reproducibility has been established. The purification process mainly consists of anion exchange in a medium of hydrochloric solution, reduction to the metallic state, floating zone melting in vacuum and wet hydrogen treatment. Several analytical methods: activation analysis, emission spectrum and atomic absorption are used to confirm the separation of main impurities in each process. Effective combination of several purification processes is selected by considering these analytical results along with the measured values of RRR_H. The anion exchange method is known to be very effective and this process consists of two steps. The first step is performed in an eluant solution of ferrous chloride and the second one in that of ferric chloride. Since the ferric chloride solution is stable against oxidation, the separation in the ferric chloride solution can be easily repeated several times. The highest value of RRR_H obtained for the purified iron is 9840 and the greater part (about 70%) of the purified iron gives a value of RRR_H larger than 7000.
The recrystallization temperatures for the iron samples with various RRR_H are measured by a isochronal annealing procedure. The sample with RRR_H of 8700 recrystallizes at a temperature of 260°C. It is shown that the recrystallization temperature is closely related to the impurity content for the same kinds of remaining impurity elements.

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Ni_52−xZn₄₈Cu_x alloys undergo a martensitic transformation from the CsCl-type ordered cubic (β₂ phase) to the AuCuI-type ordered tetragonal (α′₂ phase). The thermoelastic nature of the martensitic transformation in Ni₃₂Zn₄₈Cu₂₀ alloy was observed by an optical microscope. The microstructure of the α′₂ Ni₃₄Zn₄₈Cu₁₈ martensite was investigated by transmission electron microscopy and found to be internal twinning on the {111}⟨11\bar2⟩_fct system.

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The structure factor of liquid selenium has been measured at 265, 470 and 680°C over the range of the scattering vector from 0.5 to 30 A⁻¹ by time-of-flight neutron diffraction using epithermal pulsed neutrons generated from a 300 MeV Tohoku University electron LINAC. The characteristic oscillation of the structure factor in a high scattering vector region can be well understood in terms of a free-rotating chain molecule with a bond length of 2.38 A and a bond angle of 103°. The mean length of chain molecules becomes shorter with increasing temperature. The nearest neighbour distance between inter-molecular atoms in liquid selenium is estimated as about 3.4 A, which is close to the corresponding value in the crystalline state.

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The process of reverse transformation of the ε martensite in type 304 stainless steel was investigated by hot-stage optical and electron microscopy. It was found that the reverse transformation of the ε martensite occurs in the following way: (1) Stacking faults widely extended in the γ phase contract with increasing temperature and finally disappear. (2) The ε phase does not disappear suddenly at a certain temperature, but gradually disappears with heating. (3) Upon heating the ε phase transforms to randomly overlapping stacking faults, and finally these overlapping stacking faults contract and disappear. (4) The α′ phase does not disappear within the temperature range of the present study (below 280°C). The relation between the shape memory effect and the reverse transformation process of this alloy was discussed.

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