A study was made of crystallographic relationships in the precipitation of austenite at ferrite grain boundaries during nitriding of a ferritic Fe-1.93% Mn material at 645°C. Primary sideplates, allotriomorphs, and idiomorphs were the main precipitate morphologies observed. The austenite precipitates tended to be nucleated with a lattice orientation within about 15° of a Kurdjumov-Sachs relationship with at least one ferrite grain at the boundary of precipitation. Where there was no such lattice relationship with the other ferrite grain at the boundary, the growth of the austenite into this latter grain was preferred. The primary sideplate morphology seemingly developed only if the austenite was nucleated with its lattice within about 15° of a Kurdjumov-Sachs orientation relationship with both adjoining ferrite grain lattices. No such restriction, however, applied to allotriomorphic and idiomorphic morphologies. Primary sideplates developed at both low and high angle boundaries but allotriomorphs and idiomorphs appeared to form only at high angle boundaries.

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In order to clarify the age-hardening mechanism in a Ni-base superalloy, Udimet 520, the interaction between paired dislocations in a piled-up array and γ′ particles was investigated. The mean particle spacing for the leading dislocation was determined by the analysis of the arrangement of piled-up dislocations. The analysis also revealed that the trailing dislocation avoids γ′ particles when the leading dislocation reaches the critical position in γ′ particles. A theoretical expression for the increment of the proof stress due to aging was developed on the basis of such information; a considerably good agreement was obtained between the calculated proof stresses and the measured values.

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Invar alloys are widely used as materials for precision instruments. The practical Invar alloys are all ferromagnetic, and the ferromagnetism of these alloys often limits the scope of their application.
In recent years, therefore, considerable attention has been directed to the research and development of nonferromagnetic Invar alloys.
Cr is an antiferromagnetic material and its physical properties such as thermal expansivity and electrical resistivity change anomalously near the Néel temperature. These properties are sensibly modified by the addition of other elements. The present authors investigated the temperature dependence of the physical properties for some Cr-base primary solid solution alloys.
With the addition of Sn, the Néel temperature of Cr increases up to 2.0%Sn and then decreases gradually, and the thermal expansion coefficient below the Néel temperature becomes smaller. The Néel temperature in the Cr–Fe system decreases with increasing Fe concentration, while the thermal expansivity does not show any regular dependences on temperature and concentration.
Taking the above-mentioned results into consideration, the thermal expansivity and the magnetic susceptibility of the Cr–Fe–Sn alloys in the range of the primary solid solution have been measured.
The results show that the alloys are of the antiferromagnetic Invar type and their magnetic susceptibility is negligibly small.

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The relationship between the interaction parameter ε_2in1⁽³⁾ in a ternary liquid alloy and the valency of the composite element of the alloy was derived from an ionic solution model, composite ions of which are the ions of the composite elements of the alloy and the electron or the positive hole released from the elements.
By the approximation that the valency is equal to the effective number of free electrons, the above derived relationship gives a reasonable explanation of the relations between the valency and the previous experimental values ε_2in1⁽³⁾ for a number of ternary liquid alloy systems except for a few cases for ε_{0in Fe}^(X), etc.
The relationship is available for the prediction of the interaction parameter ε_2in1⁽³⁾ at infinite dilute solution such as ε_{C in Fe}^(X), ε_{H in Fe}^(X), ε_{Mn in Fe}^(X), ε_{N in Fe}^(X), ε_{S in Fe}^(X), ε_{N in Co}^(X), ε_{H in Cu}^(X) and ε_{N in Ni}^(X) by use of the effective number of free electrons.
A few exceptional interaction parameters, ε_{O in Fe}^(X), etc., are briefly discussed thermodynamically and from the standpoint of experimental errors.

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Tilt- and twist-type bicrystals with various misfit angles have been extended along a direction perpendicular to the boundary up to 10⁻³ strain. One composite crystal (crystal A) in the specimens is always oriented for a Schmid factor of 0.5, and another one (crystal B) is systematically rotated against crystal A.
In these specimens, deformation always starts in crystal A, and the interaction between the two crystals considerably occurs even in the low strain range less than 10⁻³. In the interaction, the continuity of slip between these two crystals plays an important role. Namely, suitable slips for relieving shear stress associated with the active slip in the opposite crystal are activated near the boundary. Considerable work hardening results from the interactions among these different slip systems even when the strain is less than 10⁻³.
The boundary strength increases with increasing misfit angle up to about 20° in both types of specimens, and then it becomes constant in the range of higher misfit-angles.

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Young’s modulus, thermal expansivity, magnetic susceptibility and electrical resistivity at −150∼400°C, and hardness at room temperature have been measured with annealed Mn–Ge alloys. Mn-5.0∼28.9% Ge alloys slow-cooled after heating at temperatures below 100°C from the solidus have distinct anomalies corresponding to their antiferromagnetic Néel points in Young’s modulus vs temperature curves. The temperature coefficients of Young’s modulus at room temperature vs composition curve exhibits a small positive maximum at 20.0% Ge, thus showing the Elinvar properties of the alloys.

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Measurements of Young’s modulus at −150∼400°C and of rigidity modulus, thermal expansion and hardness at room temperature have been carried out with Mn–Ni–W and Mn–Ni–W-Mo alloys subjected to various heat treatments and cold working. The results show that the ternary and quarternary alloys slowly cooled after heating for 1 hr at 950°C showed an anomalous temperature dependence of Young’s modulus to be associated with the antiferromagnetic \ ightleftarrows paramagnetic transformation. Young’s modulus at room temperature do not show any difference among various states of cold working and heat treating, but this value tend to increase with increasing manganese, tungsten or molybdenum content. The temperature coefficient of Young’s modulus is profoundly affected by annealing, water quenching, cold working, and reheating after water quenching or cold working, with a marked dependence on composition. The temperature coefficient of Young’s modulus in positive sign appears over a wide composition range, thus showing the appearance of the Elinvar property. The variation in rigidity modulus and its temperature coefficient with heat treatment, cold reduction rate and composition is very similar to that in Young’s modulus and its temperature coefficient. The hardness changes in a complex manner with heat treatment, cold reduction rate and composition, its Vickers hardness ranging over about 100∼600. Moreover, the corrosion resistivity of the ternary and quarternary alloy is relatively good.

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