The effect of grain size (1 to 12 μm) on the deformation kinetics in a Ti-7.4 at%Al alloy was investigated over the temperature range of 77 to 700°K. It was found that grain size primarily influences the athermal component of the flow stress, the thermal component being independent of grain size and the same as that of unalloyed titanium of the same interstitial solute content. The deformation kinetics obey an Arrhenius-type rate equation with a Gibbs free energy of activation at σ^*=0 and 0°K equal to ∼1.4eV(∼0.2 μ₀b³). It was concluded the thermal activation parameters for the plastic deformation of the alloy are the same as those of unalloyed titanium and the rate controlling mechanism is the thermally activated overcoming of interstitial solute atoms by moving dislocations.

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Different types of bi-layered scales of NiO can be formed in air on both sides of a thin nickel specimen at temperatures from 900 to 1200°C. When the black/green bi-layer is formed on one side and the black/black bi-layer on the other, a flexure of the specimen (99.9% pure) is achieved during oxidation; the former is on the convex side. When removed electrochemically from the substrate of nickel (99 or 99.9% pure), the black/green bi-layer was elongated causing bending to the opposite side. On the contrary, the black/black bi-layer formed on the 99.9% pure nickel remained straight with a negligibly small elongation as compared with the black/green bi-layer. It is found that high compressive stresses occur in the green layer, and negligibly small stresses in the black/black bi-layer. Macroscopic elastic stresses in the green layer at room temperature are estimated to be the order of magnitude 10⁹ dynes/cm². Stress gradients across the scale are roughly estimated. Discussions are given of the formation of bi-layered structures.

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Using the commercial ball bearing steel, we have studied the effects of retained austenite in the heat-treated structure on the rolling fatigue life. The results of the experiments are summarized as follows:
(1) The fatigue life depends largely on the quality of the matrix (tempered martensite), and becomes maximum when the solid solute C% is 0.5∼0.6% on quenching.
(2) In the fatigue test, both the surface and the internal hardness of the rolling part of the ball bearing steel increase to a great extent when a large amount of retained austenite is contained.
(3) A semicircular stress-affected zone is present at the rolling part in the fatigue test, where plastic flow and tempering effects are recognized in the matrix. It is also found that the retained austenite gradually decomposes during testing.
(4) The presence of the retained austenite plays an auxiliary role in improvements of the fatigue life and reduces its irregularity.

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Silver base alloys containing magnesium-, manganese- and lanthanum-oxides were prepared by internal oxidation in air at 650°C. The characteristics of erosion resistance, welding adhesion resistance, and contact resistance of these contacts have been measured under an applied voltage of 100 V and testing currents from 10 to 50 A in alternating current.
The addition of lanthanum oxide is very effective in improving the above characteristics. The contacts containing lanthanum oxide (0.5 at%La) have higher welding resistance and lower contact resistance than silver-12 wt% cadmium oxide contacts, and both contacts are equal in erosion resistance. On the other hand, although additions of magnesium and manganese oxides are not so effective as that of lanthanum oxide, the erosion resistance of magnesium oxide (1.0 at%Mg) and manganese oxide (3.2 at%Mn) contacts are comparable to that of 12 wt% cadmium oxide contacts in the high current region over 30 A. Furthermore, the change in the amount of erosion with current becomes small for magnesium-and manganese-oxide contacts.

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The effect of cold deformation on the precipitation process in Al-1.3%Mn alloy and Al-0.5%Cr alloys was investigated kinetically by hardness, electrical resistivity measurements and transmission electron microscopy. The acceleration of precipitation by cold deformation and the retardation of recrystallization by precipitation were observed. Precipitation in the low temperature region (>450°C for Al–Mn alloy and >400°C for Al–Cr alloy), where the recrystallization process progressed gradually, was inhomogeneous; the precipitates nucleated preferentially into lattice defects, such as sub-boundaries and dislocations, were globular. In the high temperature region, the forms of the precipitates were plate in the Al–Mn alloy and flat needle in the Al–Cr alloy. The acceleration of precipitation in high temperature aging by prior cold deformation was caused by the increase in preferential nucleation sites. In low temperature aging, however, not only the increase of nucleation sites but also the enhancement of diffusion of the solute atoms during recrystallization gave rise to the acceleration of precipitation.
The addition of a small amount of Si accelerated the precipitation and made the precipitates finely distributed in both non-deformed and cold-deformed specimens. This retarded the recrystallization process further. This retardation was considered to be related to the acceleration of precipitation.

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The crystallography and morphology of the metastable iron carbide in 0.79 wt%C alloy tempered at 150°C for 3 days have been investigated by means of 650 kV high voltage electron microscopy, especially by utilizing the selected microarea electron diffraction technique which enables us to take diffraction patterns from very small areas such as 500 Å in diameter. It was found that the crystal structure of the carbide is not of a hexagonal lattice, but of an orthorhombic lattice with lattice constants a_o=2.85₈, b_o=4.71₅ and c_o=4.32₉ Å (the suffix o means the orthorhombic lattice). The carbide precipitated coherently in the tetragonal martensite with orientation relationship (0\bar11)_o⁄⁄(001)_m, [100]_o⁄⁄[100]_m. High resolution bright and dark field micrographs showed that the carbide which appeared to be about 1000 Å in length is not truly a single particle but consists of smaller particles of about 50 Å size. The carbides precipitated in fine transformation twins of martensite as well as in the matrix with the same morphology and orientation relationship.

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The stress-induced acicular martensites in a Cu-14.2Al-4.3Ni (wt%) alloy were investigated extensively by the method of electron microscopy and selected area electron diffraction. As a result two types of martensites were found; one has the 18R type long period stacking order structure (β₁′), and the other the 2H type (γ′). The occurrence of the latter martensite was much less compared to that of the former. In the present paper the structure analysis and crystallographic data of the β₁′ martensite are fully described, and the results are summarized as follows. (1) The crystal structure of the β₁′ martensite was the 18R type with the stacking sequence of AB′CB′CA′CA′BA′BC′BC′AC′AB′, and its lattice parameters were a=4.382 Å, b=5.356 Å and c=38.00 Å. (2) The internal defects of the martensite was essentially stacking faults on the basal plane. But some striations were sometimes observed along the (\bar128)_β1′ plane and they were suspected to be the traces of the internal twins. (3) The habit plane of the β₁′ martensite was close to (\bar1\bar55)_β1. (4) The orientation relationship between matrix and martensite was consistent with the Kajiwara-Nishiyama relationship found in the thermally formed β₁′ Cu–Al martensite. (5) The martensite showed thermoelastic behaviour. (6) The acicular β₁′ martensite was stable under stress roughly above the Ms temperature, but the spear-like γ′ martensite was more stable roughly below the Ms temperature. (7) The crystallography of similar martensites formed in thin films was discussed in relation to that in bulk specimens.

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Stress-induced acicular martensites in Cu-14.2Al-4.3Ni (wt%) alloy were investigated by means of transmission electron microscopy and selected area electron diffraction method. As a result acicular γ′ martensites were found beside numerous β₁′ martensites reported previously, although the occurrence was quite rare. This martensite is different from the spear-like martensite thermally formed in the same alloy in several respects such as in shape, lattice invariant shear, habit plane and orientation relationship, even though both have the same crystal structure and lattice parameters. The lattice invariant strain of the martensite was found to be stacking faults on the basal plane, and a defectless region was observed at the middle of the martensite, which is in sharp contrast to the midribs in ferrous twinned martensites. The habit plane was roughly located between (32\bar1)_β1 and (32\bar2)_β1. The orientation relationship was found to be (110)[1\bar11]_β1⁄⁄(121)[0\bar12]_γ′.

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Partial molar free energy difference ΔG_X^α⁄γFe is one of the most important parameters to represent the functions of the alloying elements in steel. This parameter was defined as the free energy change accompanied by transfer of one mole of each alloying element from ferrite to austenite, and the value has been obtained from α⁄γ equilibrium compositions in the Fe–X system. In the present work, the parameters for various alloying elements were evaluated from the data on Ms^γ→α and As^α→γ temperatures of Fe–Ni–X alloys. The results show that the parameter generally changes depending on temperature, especially near the Curie point of iron, and some of the ferrite stabilizing elements, Cr, Mo, W and V act as austenite stabilizers at low temperature. The considerable temperature dependence of the parameter ΔG_X^α⁄γFe was considered to be mainly due to the magnetic effect suggested by Zener and Hillert et al.

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A dilatometric experiment of the fcc\ ightleftarrowshcp martensitic transformation in Fe–Mn–X alloys was made to determine the effects of alloying elements on the Ms^γ→ε and As^ε→γ temperatures. The As^ε→γ temperature was lowered by additions of Al, Co, Cr, Cu, Mo, Nb, Ni, Si, Ti, V, W and C, while the Ms^γ→ε temperature was lowered by alloying the above elements except Co. The parameter ΔG_X^γ⁄εFe which represents the effect of alloying element X on the relative stability of γ-iron and ε-iron near 500°K was evaluated by thermodynamic analysis of the As^ε→γ and Ms^γ→ε data. The value of the parameter ΔG_X^γ⁄εFe changed systematically with the group number in the periodic classification. Another parameter ΔG_X^α⁄εFe for α-iron and ε-iron was derived from the values of ΔG_X^α⁄γFe and ΔG_X^γ⁄εFe, and the parameter was found to change in accordance with the periodic table.

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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 for Mn–Ni–Fe alloys subjected to differing procedures of heat treatment and cold working. These measurements confirm that an anomalous change associated with the antiferromagnetic\ ightleftarrowsparamagnetic transformation appears on the Young’s modulus vs temperature curves for the ternary alloys slowly cooled after heating at 950°C for 1 hr. The Young’s modulus and rigidity modulus at room temperature does not indicate any remarkable difference by the various heat treatments, but its value shows the tendency to increase with increasing manganese or iron content. The temperature coefficients of Young’s modulus and rigidity modulus depend largely on the procedure of cold working and heat treating and also on composition. The existence of pronounced positive maximum values of temperature coefficients of Young’s modulus and rigidity modulus against composition reveals the Elinvar characteristics of the ternary alloys. The dependence of hardness on the various treatments and composition is complex. It is shown that the corrosion resistance of Mn–Ni–Fe alloys are fairly large.

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