Cu-Zn 合金贝氏体相变热力学

THERMODYNAMICS OF THE BAINITIC TRANSFORMATION IN A Cu-Zn ALLOY

对 Cu-40at.-%Zn 合金贝氏体相变温度范围内各种可能相变的驱动力进行了计算。结果表明,由于在这温度范围内存在β→β′有序相变,因而相变驱动力ΔG^(β′→α′)及ΔG^(β′→β_1′+α)随温度下降反而增大,且ΔG^(β′→α′)>0,ΔG^(β′→β_1′+α)<0;而且各成分合金β′及α′两相平衡温度 T_0,远低于 B_s 实验值,所以贝氏体相变只能按β′→β_1′+α扩散型相变进行。

The driving forces for various possible reactions within the bai-nitic transformation temperature range of Cu-40at.-%Zn alloy have been cal-culatd.The results show that because of the occurence of β→β′ordering tran-sition within the temperature range,the driving forces ΔG(?) and ΔG(?)increase inversely with decreasing temperature with ΔG^(?)>0 and △G(?)<0.Moreover,the equilibrium temperature T_0 of the two phases β′and α′is far below the experimental B_s for alloys of various compositions.Therefore,bainitic transformation in Cu-Zn alloys can only proceed as that of diffusionalreaction β′→β′_1+α.