The Acid-resistivity of Fe-Ni-Mo alloys. A series of corrosion tests of Fe-Ni-Mo alloys containing 50%, 60%, 70% and 90% Ni with varying Mo content about 1-10% and a trace of carbon, were carried out by the dip method. The corrosion was examined in 10% aqueous solutions of HNO₃ HCl and H₂SO₄ at 25° by measuring the loss in weight. The effect of Mo on the loss by HNO₃ is remarkable, though that by H₂SO₄ or HCl is very small.

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The present writers carried out experlments formerly to find the resistivity of various Cu-alloys against hydrochloric acid of various concentrations (3rd and 4th Rep. in this journal) and in this experiment, the corrosion-resistance of some copper alloys and a few nickel alloys-Nimicle F (1), Nemicle C newly prepared by one of the writers-in N/10 NaCl+0.3% H₂O₂ solutions was determined. In general, the corrosion-resistance of the alloys in the solution was the better, the higher, the nickel content. Among the alloys which contains no nickel or a little, Barberite, Silzin Bronze, Ambrac and Tempaloy were comparatively good resistant alloys especially the former two showed a good resistance in the both solutions. The corrosion-resistance of 10% Al-Cu alloy which showed an excellent resistivity in dilute hydrochloric acids was not so good as it is known in the solution and inferior to these of the alloys described above.

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From the equilibrium state of the whole system copper-nickel-silicon determined by the author, various sectional diagrams have been constructed. The following results are based on the experiments of the thermal and X-ray analyses as well as of the microscopic examination: Binary system as shown by M. G. Corson is not formed on the line Cu-Ni₂Si, and both the copper solid solution and the γ' solid solution coexist in the composition range of the Corson Alloy. Hence the second phase precipitated from the supersaturated α solid solution in the Corson Alloy is not the Ni₂Si, but the γ' and furthermore confined to the γ' only. Here the γ' is a phase formed by Ni₅Si₂ containing about 35wt.% as maximum of copper in the form of solid solution.
The structural characteristics of γ, γ' and Ni₂Si under microscope are shown by many photographs. The X-ray photographs of these phases are also given.
The κ phase existing in the Cu-Si system at the composition range of silicon from about 4.5 to 7.5% does not appear in the Corson Alloy, which is clarified by the result of the X-ray analysis. Special structures appeared in the alloy consisting of α+κ or α+κ+γ.

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In as much as the recrystallisation is the main factor of abnormal grain-growth of industrial aluminium alloys, the recrystallisation phenomena of pure aluminium were investigated in detail. Although some of recrystallisation diagram of pure aluminium have been reported, the type of the diagrams differs from each other. In chapter I are discussed factors which can affect recrystallisation, and a new diagram is constructed by the result of heating in salt bath of 0-10% deformed aluminium plates. If determined conditions were satisfactory, the diagram can be reproduced at will. This diagram shows that, the higher the heating temperature the finer the recrystallised grain size with specimens of same degree of deformation. This relation gives an account on the process of formation of new grains during recrystallisation. In chapter II are treated the problems of grain-growth which occurs after recrystallisation. This occurs generally in specimens which were subjected to a large degree of deformation and at high temperature. The author concluded that this phenomenon is induced by mutual relation between the difference in potential energy of neighbouring crystals and inter crystalline diaphram of impurity contained.

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