The martensitic transformation from the B2 to L1_o structure, and the composition and temperature dependence of the lattice parameters in the ternary Ni–Zn–Cu alloys were investigated. The axial ratio (c⁄a) of the L1_o lattice decreased slightly with increase in temperature and showed a discontinuous drop at the L1_o to B2 transformation temperature. The nature of this transformation was considered to be slightly of the 2nd order transformation, although it was almost of the 1st order. The habit plane of this martensite was also studied. The phase stability and the characteristics of martensitic transformation in the nickel base alloys were discussed briefly as a function of the electron atom ratio (e⁄a).

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Interdiffusion in an α-solid solution of Al–Ag–Zn alloys at 832 K has been investigated. The diffusion profiles have been determined, and then the diffusion paths have been drawn in the ternary composition triangle. The interdiffusion coefficients \ ildeD_AgAg^Al, \ ildeD_AgZn^Al, \ ildeD_ZnAg^Al and \ ildeD_ZnZn^Al have been determined by Matano’s method. The four coefficients have been found to be sensitive to the solute concentration. The diffusion profiles and paths have been also calculated by the solution of Fujita et al. and by the finite-difference method using the experimental values of the four interdiffusion coefficients. Good agreements have been found between the experimental and calculated both of them.

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In order to make clear the influence of vacuum annealing of specimens on intergranular hydrogen embrittlement of nickel, tensile properties and surface cracking along grain boundaries of specimens cathodically charged with hydrogen were examined. Specimens were annealed either in vacuum or in dry hydrogen gas before hydrogen charging. High susceptibility to intergranular hydrogen embrittlement and cracking of the surface was observed in specimens annealed in vacuum. Specimens annealed in hydrogen exhibited a significantly low susceptibility; they fractured in a predominantly transgranular mode, accompanied by a marked local contraction. The deleterious effect of vacuum annealing on the embrittlement was presumed to be due to the penetration of oxygen along grain boundaries during vacuum annealing. The penetration depth of oxygen was evaluated to exceed 2 mm in 10.8×10⁻³ s anneal at 873 K. These observations would have an important implication regarding hydrogen embrittlement of nickel and its alloys, since the effect of vacuum annealing has been disregarded in previous researches.

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Effect of NbC precipitation on hot deformation of austenitic stainless steels has been studied with particular emphasis on ductility. The mechanism for reducing ductility in the temperature range where NbC precipitation occurs can also explain the surface cracking mechanism of continuously cast low alloy steel slabs. The ductility trough in slow strain rate tensile tests at around 1073 K in Nb-bearing steels is accompanied by the intergranular microvoid coalescence mode of fracture. This ductility loss is induced by rather coarse NbC particles precipitated on the grain boundaries, the precipitation free zones along the grain boundaries and the dynamic precipitation of fine NbC particles within the grains. That is, when an external stress is applied, the strain will be concentrated within the soft layers of precipitation free zones by the matrix strengthening due to fine dispersion of NbC. This will lead to the decohesion of the NbC/matrix interfaces on grain boundaries, resulting in the intergranular microvoid coalescence.

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The high temperature oxidation behaviour of 18Cr–8Ni austenitic steel has been studied in presence of Na₂SO⁴ and transition metal salts, e.g. NiSO₄, CoSO₄, Cr₂(SO₄)₃, (NH₄)₂MoO₄, NaVO₃ or Na₂WO₄ in the temperature range of 923–1273 K in air.
The steels coated with a mixture of Na₂SO₄+NiSO₄ and Na₂SO₄+CoSO₄ show higher corrosion rates than either the Na₂SO₄ coated or transition metal sulphate coated steel at 923 K. This has been attributed to the formation of low temperature eutectics. At 1273 K, except the Cr₂(SO₄)₃ or CoSO₄ coated steel, the steel coated with all other salts, e.g. Na₂WO₄, NaVO₃ or (NH₄)₂MoO₄, have much higher corrosion rates than the Na₂SO₄ coated steel. The decomposition of these salts into volatile oxides, e.g. WO₃, V₂O₅ or MoO₃ seems to be the sole reason for catastrophic oxidation. A direct oxidation or sulphidation cum fluxing mechanism is adequate to explain hot corrosion. The scale morphology as predicted from mechanistic considerations is in fairly good agreement with the observed morphology.

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Water on an aluminium surface was liberated by stepwise heating of the sample in an infra-red (IR) radiation furnace, and determined by the coulometric titration method after conversion into ammonia. Adsorbed water on the alumina layer formed on the aluminium surface was first removed at 373 K, and combined water in the layer was liberated between 673 and 873 K. No water liberation could be found at 473 and 573 K, but some hydrogen was generated at 573 K by the reaction between the water and aluminium. The amount of each kind of water increased appreciably by the storage of the samples in an hygrostat after their surface treatments. However, the amounts of water liberated between 673 and 873 K were nearly constant, when the samples were analysed immediately after their surface treatments. Therefore, the correction of combined water for the determination of hydrogen in the metal was partly possible, when the sample was heated by two steps. After removement of adsorbed water at 373 K, the sample was heated at 873 K for the determination of both hydrogen and water, and the amount of 873 K water measured separately was deducted from the previous result. However the error due to the reaction between water and the metal found at 573 K cannot be corrected irrespective of the method of hydrogen determination, though it may be reduced by taking a large amount of the sample.

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The volatilization in the Al–O–C(–Si–Fe) system have been investigated mainly by thermal gravimetry in vacuum for four cases; (1) aluminum oxycarbides, (2) mixtures of alumina and carbon with and without additives (iron oxide, silicon nitride and silicon carbide), (3) mixtures of alumina and aluminum carbide or silicon carbide and (4) mixtures of alumina, silica (mullite), iron oxide and carbon. Al₂OC evaporated essentially congruently, whereas Al₄O₄C evaporated incongruently; α-Al₂O₃ was formed in addition to vapors. The volatilization reaction between alumina and carbon was found to be enhanced remarkably when iron was added, unchanged by SiC addition and prevented slightly in the presence of Si₃N₄. The mixtures of alumina and carbide volatilized at lower temperatures than did those of alumina and carbon. These features are discussed in terms of the equilibrium pressure in the light of previous results of reaction experiments focussed upon the oxycarbide formation.

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In order to understand the temperature and composition dependence of the interdiffusivity of CaO–FeO in the liquid CaO–FeO–SiO₂ slag in equilibrium with solid iron, electrochemical measurements have been carried out at 1573 to 1673 K. The experimental technique was the chronopotentiometry at constant currents supplied to the following cell:
solid Fe/liquid CaO–FeO–SiO₂/soid Fe.
The results at a constant FeO mole fraction of 0.26 are expressed as follows;
(Remark: Graphics omitted.)
and
(Remark: Graphics omitted.)
where B is the molar ratio, CaO/SiO₂. These results are compared with the values estimated from tracer diffusivities, D_Ca and D_Fe.

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Carbon redistribution in the liquid ahead of planar and paraboloid interfaces of flake graphite cast iron unidirectionally solidified was calculated. The fraction of carbon diffusion in the liquid f in eutectic solidification is related to the growth rate R, the intergraphite spacing λ, the diffusion coefficient of carbon in liquid D and undercooling at the solidification front ΔT₀, as
fλR=0.0032DΔT₀
This equation is approximately valid both for the planar and paraboloid interfaces at different temperature gradients. The calculated f decreases with a decrease in the growth rate. This corresponds to the empirical fact that the paraboloid protrusions become more prominent with a decrease in the growth rate. The fraction of carbon diffusion through austenite sheath (1−f) in eutectic solidification increases with increasing growth rate. The protrusions often appearing on the slowly solidifying interface are attributed to a less undercooling at the interface, where carbon diffuses both in the liquid and the austenite, than that in the liquid.

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