对x_(Al)=0.24合金贝氏体相变的两种机制的相变驱动力ΔG~(p_1→a’)及ΔG~(β_1→β_2~(+a))进行了热力学计算,结果表明,在贝氏体相变温度范围680—750K内,ΔG~(β_1→α’)>0,这说明贝氏体相变的开始不可能按β_1→α’的切变型机制进行,在700K只产生5％的α时,α的成分至少降到x_(Al)~α=0.204,才能使ΔG~(β_1→β_2~(+α))<0,而在750K,则至少需满足x_(Al)~α≤0.209,才有ΔG~(β_1→β_2~(+α))<0,说明贝氏体相变须按β_1→β_2+α扩散型机制进行,且转变温度不同,所需扩散量也不同。
Two driving forces △G~(β_1+α') and △G~(β_1→β_2+α) for the baintic transformationhave been calculated for a Cu-24at.-% Al alloy. Results reveal △G~(β_1 →α')> 0 within the trans-formation temperature range 60--750 K. Therefore, the bainitic transformation cannot beinitiated by the β_1→α' shearing mechanism. On the other hand, the driving force △G~(β_1→β_2+α)to produce 5% of the α becomes negative only when the composition of the α satisfiesx_(Al)~α≤0.204 at 700 K or x_(Al)~α=0.209 at 750 K. So the bainitic transformation can only proceedby β_1→β_2+α diffusional reaction with diffrent diffuson amount at different temperatures.
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