The effect of quenched and tempered structure on the diffusion coefficient and solubility of hydrogen in high-strength alloy steels, such as Cr, Cr–Mo, Ni–Cr and Ni–Cr–Mo steels, have been investigated at room temperature by means of electrochemical permeation technique.
The diffusion coefficient and the solubility of hydrogen vary with the structure of the steel; the former shows a minimum, when the steels are quenched and tempered at 300°C except for one with high Mo content, while the latter exhibits a maximum at that temperature. In the case of steels having comparatively higher Ni, Cr and Mo contents, the structure of bainite plus martensite obtained by furnace cooling from the temperature above Ac₁ have lower values of diffusion coefficient which are comparable with that of the as-quenched martensitic structure. The dependence of hydrogen diffusion on the quenched and tempered structure can be explained by postulating that both the lattice imperfections, such as dislocations, lattice vacancies and subgrain boundaries introduced by the martensitic and/or bainitic transformation, and the interfaces between the ferrite phase and carbide precipitates, provide regions for the occupancy of hydrogen.

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The thermodynamic activities of iron in iron-nickel alloys have been determined by e.m.f. measurements on solid-electrolyte oxygen concentration cells over the temperature range 750–1150°C.
Pt/Fe, FeO//ZrO₂·CaO//Fe–Ni alloy, FeO/Pt.
The activity of iron in the Fe–Ni system exhibits slightly positive departures from ideal solution behavior in the iron-rich alloys and negative departures in the nickel-rich alloys. The activities of nickel, deduced from the Gibbs-Duhem equation, indicate negative departures from ideality in the entire composition range.
The relative integral molar excess entropies are positive for all the compositions studied. However, a consideration of the magnetic factors suggests that the configurational excess entropies are negative and that the solid solutions are non-random.
The heats of mixing vary from the endothermic to exothermic values with increasing nickel content. It is inferred that the non-random behavior suggested by the presumed configurational excess entropies is clustering at the iron-rich compositions and short-range ordering at the nickel-rich compositions.

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Flow stress measurements were made on single crystals of Ni₃Ge with several different orientations. Slip systems were determined by two-surface trace analysis, and dislocation arrangements due to deformation were observed by transmission electron microscopy. The yield stress increases with increasing temperature in the temperature range of −196∼800°C where {111} slip operates (positive temperature dependence), but it decreases as {001} slip commences. Critical resolved shear stress for {111}⟨10\bar1⟩ slip is orientation-dependent. The positive temperature dependence is pronounced even below room temperature, and the yield stress nearly doubles as the temperature is raised from −196 to 27°C. Electron microscope observation on dislocation arrangements in the specimens deformed at −196 and 27°C has revealed that the mobility of screw dislocations decreases with increasing temperature. These observations indicate that the positive temperature dependence of the yield stress is controlled by the mobility of screw dislocations. This decrease of mobility leading to the positive temperature dependence of the yield stress can be explained by thermally activated cross-slip of screw dislocations from the (111) plane to the (010) plane.

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Three kinds of Fe-1.0 wt%C binary mixed powder compacts, containing electrolytic, atomized and reduced iron powders with different H₂ losses, were used in order to examine the process of carbon diffusion into iron and the decarburization during sintering in a vacuum of 1.3332×10⁻³ Pa, by means of the dilatometric method, measurement of the degree of vacuum, and carbon analysis.
The results obtained are summarized as follows: All of the three kinds of Fe-1.0%C binary mixed powder compacts showed the expanding (swelling) phenomena after the α→γ transformation during heating, and the expansion curve in dilatation well agreed with the combined carbon concentration curve. The vacuum measurement revealed that the amount of gas discharge from the specimen with the reduced iron powder was considerably larger than that of the other specimens, while its dilatational expansion was minimum. Therefore it was confirmed that the expanding phenomena did not occur by the gas discharge but by the carbon diffusion into γ-Fe.

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Transmission electron microscopic observations were made on the recovery process of lattice defects in cementite in high carbon steels annealed after 92% cold rolling. Thermomagnetic and X-ray analyses were also performed as additional examinations.
No observable change in the defect structure of cementite occurs at temperatures below about 400°C. Annealing at higher temperatures results in the disappearance of the moiré pattern, a considerable decrease of dislocation density and the formation of well-developed subboundaries. Above about 600°C, these defects disappear gradually with the progress of spheroidization. These results suggest that the recovery of lattice defects in cementite is caused by polygonization accompanied by climbing or cross slipping of dislocations.

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