(1) コルソン合金のNi₂Si濃度を5.89％, 4.94％, 3.58％及び2.49％の4通りに變じて.950°燒入後500°,450°及び400°に於て時効硬化せしめたる場合のVi-ckers硬度,抗張力,補正抗張力,伸長率及び均質伸長率の變化を測定した,又Ni₂Si5.89％及び4.94％の試料については,時効後の電氣抵抗の測定をも併せ行つた.
(2) 硬度の變化は時効温度の高き程速かに起る.硬化値は時効温度ゐ高すぎない範圍ではNi₂Si濃度の大なる場合程,又時効温度の高い程大となる.但しNi₂Si濃度が大で時効温度が高すぎると却つて最高硬度が小となる.
從て硬度を有効に十分増大せしめる爲の時効最適温度は,Ni₂Si濃度に左右せらるるもので,Ni₂Si5.89％では450°,その他は500°が良く,一般的に見てNi₂Siの濃度大なる程最適温度は低くなる.
(3) 抗張力及び補正抗張力は共に時効温度高き程その變化の速さ大となる.而してNi₂Si濃度大なる程抗張力及び補正抗張力は大となる.硬度の變化と對照すると,抗張力及び補正抗張力は,硬度が既に極大値を超えて軟化して居る時期に於ても依然として増大して居るてとが認められ,500°時効に於ける抗張力及び補正抗張力の極大點の出現が硬度の極大に比し時聞的におくれて現れるものであることが認められる.而してこのズレはNi₂Si濃度の大なる場合程著しく現れる.Ni₂Si濃度2.49％のものでは殆どこのズレが認められない.
(4) 伸長率及び均質伸長率の變化に於ても,時効温度高き程その變化は速く起る.均質伸長率ではNi₂Si濃度大なる程その減少も大であるが,通常伸長率ではこの關係は必ずしも一定しない均質伸長率では500°時効に於てNi₂Si5.89％及び4.94％のものに就てのみ極小點が現れ,3.58％及び2.49％のものでは現れないが,通常伸長率には何れのものについても500°時効に於て極小點が現れる.
又伸長率及び均質伸長率の變化に於ても,抗張力の場合の如く硬度の變化との間に時間的なズレが著しく現れるものである.
(5) 以上によつて明かなる如く,機械的性質の時効に件ふ變化は時間的に,硬度,抗張力,伸びに於て一様でなく,時間的のズレがある,從て硬度のみを測つてもこのズレを考慮に入れないと他の性質を豫測することは出來ない.この關係に就ては次報でくわしく論じてみたい.

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The heterogeneous equilibria in the solid state of Cu-Sb-Ni alloys have been carefully studied by differential dilatometric measurements and microscopic examination, and the equilibrium diagram of the complete ternary system Cu-Sb-Ni has been constructed by aid of many sectional and isothermal diagrams. The main points in the present investigation may be cited as follows:- (1) In the solid there exist α, β, γ_n, γ_c, δ_n, δ_c, θ_n, θ_c and η phases. (2) Mono-variant reactions are 22, as shown in Table 1, in which 15 are binary eutectoid lines and 7 are binary peritectoid lines. (3) These mono-variant reactions meet at six points at which position the following non-variant reactions occur:
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(4) The binary peritectoid reaction a+β_??_δ of the, Ni-Sb system changes, by addition of a small amount of Cu, to the binary eutectoid reaction β_??_a+δ_n. (5) The binary peritectoid reaction β+γ_??_θ of the Cu-Sb system also changes, by addition of a small amount of Ni, to the binary eutectoid reaction β_??_θ_c+γ_c. (6) Decomposition temperatures of β phase of the Ni-Sb system lowers by addition of Cu, reaching room temperature nearly at the composition 22.5%Cu, 45.0%Sb, 32.5%Ni, and by a further addition of Cu, the decomposition temperatures rises again. (7) Combining the results of the previous report, all the heterogeneous equilibria in the ternary system, Cu-Sb-Ni, have been shown graphically as well as in a tabular form.

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The mechanism of the decarburization of steel and cast iron was studied in the following three cases.
1. Steel of, the austenitic structure : The distribution of carbon concentration was observed for commercial pure steel decarburized at a temperature above 900°. The diffusion coefficient of carbon in gamma iron was determined by the Fick's method, and the activation heat of diffusion independent of the decarburizing temperature was obtained by Langmuir and Dushman's equation.
2. White cast iron of the mixed structure of austenite and cementite: An irregular carbon distribution in white cast iron after decarburization was clearly explained by the diffusion theory of carbon using the above determined diffusion coefficient of carbon in gamma iron.
3. Steel gave alpha iron bands on its surface: When steel was decarburized at a temperature below 900°, alpha iron bands appeared clearly on its surface. This phenomenon was explained by the diffusion theory of carbon and the activation heat of diffusion was calculated for alpha iron in the same way as for gamma iron and was found to be independent of decarburizing temperature and decarburizing method.
From thepresent study, it seems that the decarburization occurs by the following mechanism ; in the surface of steel or cast iron the carbon content decreases down to zero to take an equilibrium with surrounding gas; if the composition of gas is in proper condition, the carbon diffuses in atomic state from interior to the surface, not only in austenite but also in alpha iron, and then it reacts with oxidizing gas.

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