变形温度对形变强化相变完成时临界应变量的影响

Influence of deformation temperature on the critical strain for completion of DEFT

利用“形变强化相变”机制研究了低碳钢过冷奥氏体在740℃和780℃,10s-1变形时的变形温度对相变完成时临界应变量εc的影响。结果表明,变形温度对εc和组织演变的影响很大。在740℃和780℃变形时,εc分别为0.96和1.39,变形温度降低明显促进了相变。变形温度对εc的影响在组织演变上主要表现为铁素体形核地点的不同。740℃变形时,铁素体由奥氏体晶界形核过渡到以形变带形核为主,形核速率极高;780℃变形时,铁素体由奥氏体晶界形核过渡到在铁素体/奥氏体相界面前沿高畸变区快速形核。

Influence of deformation temperature on the critical strain for completion of DEFT was investigated by using deformation enhanced ferrite transformation when the undercooled austenite in a low carbon steel was deformed at 740℃, 780℃ and strain rate of 10s^-1. The results show that deformation temperature has a strong effect on εc and microstructural evolution, εc are 0. 96 and 1.39 when the undercooled austenite was deformed at 740℃ and 780℃, respetively. Ferrite transformation is obviously accelerated at low deformation temperature. The effect of deformation temperature on εc is exhibited on the different nucleation sites of ferrite during the microstructural evolution. Ferrite has the very rapid rate for nucleation when undercooled austenite is deformed at 740℃, because ferrite chiefly nucleates at the deformation bands as soon as prior austenite grain boundaries are filled with transformed ferrite. However, ferrite nucleates rapidly at the front of the phase boundaries between ferrite and austenite after prior austenite grain boundaries are full of tranformed ferrites when undercooled austenite is deformed at 780℃.