Fe-8mass%Cr合金の高温相組織と焼結機構

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Phase constitution of Fe-8mass%Cr alloy at elevated temperatures and the relationship between phase constitution and sintering mechanism were investigated by means of the model examination of two twisted wires.<BR>The ferritic structure of Fe-8mass%Cr alloy at room temperature easily transforms to full austenite during heating to elevated temperatures. The matrix, however, changes the structure from γ to (δ/γ) two phases in the temperature range of 1463-1523K and then to δ single phase above 1523K. During holding at the (δ/γ) two phases region, the δ volume fraction increases until 7.2ks and levels off after that, because the δ/γ ratio reaches the equilibrium state at a given temperature through the re-distribution of Fe and Cr atoms into δ and γ phases.<BR>Sintering of two twisted wires in δ or γ single phase regions follows a linear relationship with a slope of 1/5 (m=5);log(x/a)=K+(1/m)⋅log(t), where x is neck width, a is wire radius, t is sintering time, K and m are constants. The slope 1/5 indicates that volume diffusion mechanism controls the sintering in single phase regions. On the other hand, the slope of the linear relationship in (δ/γ) two phases region becomes larger than 1/5 (m<5), because not only sintering but also γ phase decmmnnsit.inn occurs dnrine early st.aee of isothermal hnldine.
社団法人粉体粉末冶金協会の論文