The rate of initial oxidation of manganous oxide in air was observed by the thermogravimetric measurements in the temperature range between 380 and 675°C. The rate of this process follows direct logarithmic, inverse logarithmic and cubic rate laws successively from the very first stage. The height of the potential barrier for the electron tunneling from MnO through Mn₂O₃ was estimated to be about 0.1 eV from the results of the direct logarithmic region. The electric field strength across the oxide film in the next initial stage was estimated to be about 10⁷ V/cm from the results of the inverse logarithmic region. The activation energy for the diffusion of oxygen ion in Mn₂O₃ was obtained from the results of the inverse logarithmic and cubic regions to be 1.3 and 1.2 eV, respectively. These experimental results have confirmed that the Mott-Hauffe-Ilschner mechanism can be applied to the initial oxidation of manganous oxide.

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The experimental and theoretical studies on a large scale composition fluctuations above the α-α′ solvus curve were made using small angle X-ray scattering near the critical temperature for Al-39.16 at% Zn alloy. Above the critical temperature (T_c1=351°C), we observed weak satellite reflections whose intensities increase near T_c1. This result is explained in terms of electron density-density correlation function. The distribution of solute atoms is periodically fluctuated with a characteristic wavelength in the alloy. X-ray scattering near the transformation temperature of the α and β decomposition (T_c2\simeq275°C) is also discussed.

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The effect of composition on SCC of austenitic stainless steel has been investigated in various boiling MgCl₂ solutions. The stress applied was a constant load of 25 kg/mm². The relation between the boiling point of MgCl₂ solution (concentration of MgCl₂) and the time to fracture was determined. The results obtained are as follows:
(1) Commercial stainless steels show the maximum susceptibility to SCC over a certain concentration range of boiling MgCl₂ solutions.
(2) The sensitized stainless steel suffers intergranular stress corrosion cracking in low-concentration boiling MgCl₂ solutions.
(3) Based on a study of the effect of component elements, it is found that the boiling point of MgCl₂ for the minimum time to fracture is shifted to lower temperatures in presence of C and Si and to higher temperatures in presence of Mo, N, P, Cr and Cu, while Ni decreases the susceptibility to SCC over the whole temperature range investigated.
(4) The time to fracture consisted of the induction time and the propagation time. The mechanism of SCC is also discussed here.

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Tensile tests were performed on bicrystals and corresponding component crystals of Al-3%Cu heat-treated to different stages of ageing, that is, those of supersaturation, intermediate phase formation and stable phase precipitation. The stress-strain curves were analysed from the point of view of the effect of ageing and crystal orientation on deformation. The following results were obtained: (1) The strength of a supersaturated solid solution is determined by the compatibility condition and the dislocation pile-up mechanism at a grain boundary. (2) No simple relationship was established for both intermediate phase formation and stable phase precipitation. (3) The “grain boundary strength” Δσ_ε of the supersaturated solid solution shows a parabolic relation against strain. (4) The “grain boundary strength” for the intermediate phase initially shows a parabolic strain dependence, but decreases to a negative value as deformation proceeds. (5) The “grain boundary strength” for the stable precipitation shows a parabolic strain dependence similar to that at the supersaturation stage.

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Oxidation behaviors were investigated on Fe–Cr alloys of different composition at 900°C as a function of oxygen partial pressure which was controlled with H₂–H₂O ratio. In the early stage FeCr₂O₄ was found even under low oxygen partial pressures where FeCr₂O₄ is thermodynamically unstable. In the atmospheres where only Cr is oxidized, the oxidation rate of alloys containing 15% Cr or more was considerably higher than that of 5 and 10% alloys. This is probably attributed to the difference in diffusion rate of Cr in high Cr alloys (α-phase) and in low Cr alloys (γ-phase). A similar technique was applied to Fe–Ni–Cr–Si and Fe–Ni–Cr–Ti alloys and essentially the same results as Fe–Cr alloys were obtained, though the result on the alloy containing Si suggested the additional double oxide formation from iron and silicon oxides.

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Diffusion coefficients of chromium, manganese, and nickel in molten iron were measured by the diffusion-couple method at 1550 and 1600°C in the composition range of up to about 5%.
(1) Diffusion coefficients of Cr, Mn, and Ni in molten iron obtained are as follows:
D_Cr(1550°C)=3.04(±0.37)×10⁻⁵cm²⁄sec,
D_Cr(1600°C)=3.42(±0.40)×10⁻⁵cm²⁄sec,
D_Mn(1550°C)=4.37(±0.36)×10⁻⁵cm²⁄sec,
D_Mn(1600°C)=4.96(±0.61)×10⁻⁵cm²⁄sec,
D_Ni(1550°C)=4.67(±0.45)×10⁻⁵cm²⁄sec,
D_Ni(1600°C)=5.59(±0.34)×10⁻⁵cm²⁄sec.
(2) A close correlation was found between the diffusivity D_j and the standard free energy of solution ΔF_j⁰ for the elements dissolved in molten iron; the diffusivity D_j increases with an increase of ΔF_j⁰.
(3) Comparison of the above-mentioned finding with the previous results on the diffusion in molten carbon-saturated iron suggested the same functional relationship between the diffusivity and the standard free energy of solution, irrespective of whether carbon is contained in the solvent iron or not.

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E.M.F. of a galvanic cell with the solid electrolyte (ZrO₂+CaO) was measured to determine the activities of gallium in the temperature range of 800∼1000°C and the composition range of 0∼58.9 at% Ga for solid Co–Ga alloys, and thermodynamic functions were derived from the results. The cells used were as follows:
Pt, Re, Ga, Ga₂O₃/ZrO₂(+CaO)/Fe, Fe_xO, Pt
Pt, Re, Co–Ga alloy, Ga₂O₃/ZrO₂(+CaO)/Fe, Fe_xO, Pt.
Activities of gallium showed large negative deviations from Raoult’s law in the whole composition range investigated. Activity changes with composition in cobalt-rich α solid solution were small, but very large in the β(CoGa) phase. Activities of cobalt showed very small positive deviations from Raoult’s law in the α solid solution, but very large negative ones in the β phase. Activities of gallium and free energies of formation showed larger values than those of Ni–Ga alloys. The solubilities of gallium in cobalt in the temperature range of 800∼1000°C were found to be larger than those shown in the phase diagram of Elliott. Standard free energy of formation of Ga₂O₃(s) was shown by
ΔG_Ga2O3⁰=−260760+78.6T(°K)±400cal/mol
in the temperature range of 720∼1030°C.

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The crystal structure and phase transformation of the vanadium-oxygen alloys with O/V<0.28 were studied by combined methods of transmission electron microscopy, selected-area electron diffraction, X-ray powder diffraction and calorimetry. The interstitial oxygen atoms in the structure of V₁₂O–V₈O, which is usually termed as V₉O or α′ phase, occupy regularly special octahedral sites in the bct metal subcell with the axial ratio c⁄a\simeq0.96. The superlattice of the metal subcell has the lattice parameters A=B=4a and C=6c. The oxygen arrangement is characterized by the occurrence of periodic out-of-steps with the spacing 3c along the [001] direction. The ordered structure transforms at 519°C into the partially disordered β phase with the bct metal subcell of c⁄a\simeq1.07. A revised partial phase diagram is proposed.

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An electrolytic cell was devised to differentiate the sources of the overpotential encountered in Pt-oxygen electrode reactions in the molten Na₂O–B₂O₃ system. The result shows that the overpotential due to a concentration gradient of Na₂O is negligible at steady state conditions at 865°C.

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The decomposition process of Cu-4wt% Ti alloy during aging at low temperatures, 200–260°C, and at higher temperatures, 300–450°C, has been investigated by means of X-ray small-angle scattering technique.
At the initial stages of aging at the low temperatures, spinodal decomposition takes place and gives the sinusoidal composition modulations in the solid solution. The rate of amplification of composition waves is well in accord with the kinetics of spinodal decomposition. At the later stages of the aging, the sinusoidal composition wave transforms into a step-like one with a well-defined interface between the matrix and the solute-rich regions. The critical temperature, below which the alloy is allowed to decompose spinodally, is estimated to be about 350°C.
At higher temperatures, 300–450°C, the zone-complex are formed during aging for 1 min and thereafter the aggregation of the zone-complex is a main process at 300–400°C. At 450°C, the amount of the inner-zone of the zone-complex still increases during further aging, and the solute concentration in the matrix is decreased. It is found that X-ray side-bands obtained from the alloy aged in the high temperature range are not directly associated with the spinodal decomposition of this alloy.

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