The lattice diffusion and the grain boundary diffusion of copper in γ-iron were measured in the temperature range from 1105 to 1210°C by the residual activity method with radio-active tracer ⁶⁴Cu. The experimental penetration profiles were analysed by the instantaneous source model of grain boundary diffusion proposed by Suzuoka. The temperature dependence of the lattice diffusion coefficient D_l and the grain boundary diffusion coefficient D_gb are expressed by the following equations:
D_l=4.16×10⁻⁴exp(−305.0kJ·mol⁻¹⁄RT)m²s⁻¹
D_gb·δ=4.27×10⁻¹³exp(−167.8kJ·mol⁻¹⁄RT)m³s⁻¹.

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In order to understand the role of Ni in enhancing the sintering of Fe–Ni powder compacts, the grain boundary diffusion coefficient of ⁶³Ni in γ-Fe is determined in the temperature range from 1153 to 1287°C by the residual-activity counting method using the instantaneous source model proposed by Suzuoka.
The results are expressed as follows:
Volume diffusion: D=1.09×10⁻⁴·exp(−296.7kJ·mol⁻¹⁄RT)m²⁄s
Grain boundary diffusion: D′=24.1×10⁻⁴·exp(−176.2kJ·mol⁻¹⁄RT)m²⁄s.

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The morphologies of couplings of thin-plate martensites in an Fe-31%Ni-0.28%C alloy were investigated by means of transmission electron microscopy and they were discussed in terms of the phenomenological martensite theory. The results obtained are as follows.
(1) The morphologies of couplings such as spear, wedge, kink, diamond, composite spear and zig-zag types were observed. These couplings consisted of variants in the same plate group and some of wedge and zig-zag type couplings were found to be composed of variants in different plate groups.
(2) The observed junction planes of couplings of variants in the same plate group were a {110}_γ plane in a spear type, a {144}_γ plane in a wedge type and a {100}_γ plane in a kink type. The junction planes of the couplings of variants in the same plate group and those in different plate groups were found to be a bisecting plane of two habit planes.
(3) From the average form of the shape strain matrices of the variants, it is considered that the spear, wedge, diamond and zig-zag type couplings are self-accommodating, whereas the kink type is not.
(4) The diamond and composite spear type couplings were the composite of some of the three fundamental types, spear, wedge and kink ones.
(5) The junction planes of couplings of variants in the same plate group could be derived from the planes of intersection of the strain ellipsoids of the variants and the sense of the shear directions of the shape strains of the variants at the junction planes.

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Close-packed hexagonal ε and body-centered cubic (or tetragonal) α′ martensites in an Fe-12.0%Mn-0.48%C (wt %) alloy have been examined by optical and electron microscopy and electron and X-ray diffractions. The α′ martensites are clearly shown to form in ε martensite bands via the γ→ε→α′ transformation process, having six variants of orientations in one ε martensite. They make three pairs by two variants which contact to each other forming a junction plane. Two surface trace analysis shows that the junction plane is parallel to a {1\bar100}_ε (or {11\bar2}_γ) plane which is perpendicular to the (0001)_ε (or (111)_γ) habit plane of the related ε martensite bands, and that habit planes of the paired two α′ martensites deviate from the {1\bar100}_ε junction plane in opposite ways by about 7°. Both the habit planes and crystallographic axes of the paired two martensites are twin-related to each other martensite with respect to the {2\bar11}_α′ twin plane and also to the junction plane. (011)[01\bar1]_α′ planar defects are found by electron microscopy in α′ martensites. The twin-related habit planes and crystallographic axes of paired two α′ martensites are well explained by a phenomenological calculation for the ε to α′ transformation using the (0001)[1\bar100]_ε (or (011)[01\bar1]_α′) lattice invariant shear observed by electron microscopy and the lattice parameters determined by X-ray diffraction.

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Young’s modulus at high temperatures, thermal expansion, rigidity modulus, hardness and tensile strength at room temperature have been measured for Mn–Ni–Ti and Mn–Ni–Zr alloys subjected to various heat-treatments and cold-working. The Young’s modulus vs temperature curves of the annealed ternary alloys indicate marked changes that are associated with the phase transformation and the antiferromagnetic to paramagnetic transformation. The temperature coefficient of Young’s modulus at room temperature is largely affected by annealing, cold-working and reheating after cold-working and also composition. The temperature coefficient vs composition curves has a positive maximum, revealing the Elinvar characteristics. Young’s modulus, hardness and tensile strength at room temperature of the Mn–Ni binary alloys increase with addition of Ti or Zr.

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Eutectic Fe–C and Fe–C-0.2%P gray cast irons were solidified in glass to confim homogeneous distribution of eutectic cells and their microstructures were analysed by quantitative metallography.
In the first experiment, the specimens being control-cooled were quenched in water at various stages of the eutectic solidification. The number of eutectic cells in unit volume as well as the average radial growth rate of the cells were roughly constant during the solidification after the recalescence. Based on these facts, the solidification fraction was well defined by the growing cell radius and the number of cells in unit volume. In the second experiment, the eutectic irons were solidified completely at different cooling rates resulting in various degrees of undercooling, and the radial growth rate of eutectic cells was evaluated from the number of interceptions of a scanning line with cell boundaries in unit length and the solidification time using the relation obtained in the first experiment. The radial growth rate was nearly proportional to the degree of undercooling and the growth rate of eutectic cells in the iron containing phosphorus was lower than that in pure Fe–C iron at any degree of undercooling.

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