The elastic energy due to a periodic distribution of two kinds of variants of the martensitic phase is calculated by means of the reciprocal lattice method. It is found that the elastic energy is proportional to (λ⁄2Z₀)², where λ is a period of 2 variants and 2Z₀ is the thickness of martensite. Comparison with the experimental results is done.

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Stress-strain curves for iron single crystals deformed by a shearing method varied significantly with the shearing plane and direction. When the shearing plane was the (112) plane, three-stage hardening occurred at 300 and 195 K. On the other hand, for crystals sheared on the (101) plane, stress-strain curves showed the parabolic type. However, the dislocation structures were similar for crystals sheared both on the (112) and (101) planes. The distribution of dislocation in deformed crystals was inhomogeneous ; the cell structure having cell walls approximately parallel to ⟨111⟩ developed. The three-stage hardening behavior for crystals sheared on the (112) plane depended markedly on shearing direction. The work hardening of stage II increased as the shearing direction diverged from the slip direction [11\bar1]. This change for hardening rate in stage II with shearing direction was closely related with the stress component ratio of secondary to primary slip systems. In the crystals sheared at 77 K, where the stress-strain curves showed the parabolic type for both (101) and (112) shearing planes, the dislocation arrangement was uniform and screw dislocation was predominant.

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The structure of quenched Ni₃(Mo, Ta) alloys containing 2 and 5 at% Ta was investigated by transmission electron microscopy. It was found that the DO₂₂-type ordered phase was formed in the Ni₃(Mo, Ta) alloy containing 5 at% Ta quenched from 1300°C. The changes in structure, interaction energy and strain energy with increasing Ta content are discussed. It is described by using a tetrahedron model that regions which take Ni₃Mo-type tetrahedron in FCC lattice site will either extend or increase in number, or both with increasing Ta content. It has been deduced that the addition of Ta to Ni₃Mo alloy causes the V₂/V₁ to decrease, and by the addition of atoms having an atomic radius larger than that of Mo atoms, the tendency of the formation of the DO₂₂-type ordered phase increases.

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A quarter of the century ago Bardeen and Herring showed that vacancies diffuse more “effectively” than atoms because the atoms are impeded by the occurrence of correlation. This difference in behavior is not evident in the elementary act of the vacancy mechanism of diffusion (the exchange of a vacancy with a neighboring atom of metal 1) which leads to equal but opposite interchange fluxes, I₁°=−I_v°. For tracer diffusion in pure metal 1, however, the effective gross fluxes are J₁°=−fJ_v°, where f is the correlation factor. This result is obtained analytically and has been corroborated by a computer simulation of tracer diffusion. For steady-state isothermal electromigration in pure metal 1, the net fluxes are J₁=−f₁J_v, clearly demonstrating the impeding action of correlation on the diffusion of atomic species. The implications of the latter result for present diffusion theory are briefly discussed.

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