42CrMo钢动态再结晶的临界条件

Dynamic recrystallization critical conditions of 42CrMo steel

采用Gleeble-1500热模拟试验机对挤压态42CrMo钢进行等温热压缩实验,研究了在温度为1123～1348 K,应变速率为0.01～10 s-1条件下的动态再结晶行为。流变应力曲线对比分析表明:42CrMo钢在0.01～1 s-1的低应变速率下(除1 s-1和1123 K)发生动态再结晶型软化,在1～10 s-1的高应变速率下(含1 s-1和1123 K)发生动态回复型软化。采用加工硬化率的方法处理流变应力数据,结合lnθ-ε曲线的拐点及2(lnθ)/ε2-ε曲线的零点判据,研究42CrMo钢热塑性变形中动态再结晶发生的临界条件。结果表明:所有压缩试样均发生了动态再结晶;增加应变速率及降低变形温度会抑制动态再结晶的发生。进一步引入表征动态再结晶临界条件的临界应变模型,建立了临界条件与各热力参数之间的数学关系。验证表明该模型相对误差不超过7.8%。

Dynamic recrystallization behavior of as-extruded 42CrMo alloy during hot compression deformation was investigated at 1123- 1348 K and strain rate of O. 01-10 s^-1 on a Gleeble-1500 thermo-simulation machine. Through comparison of flow stress curves under different deformation conditions, it is found that in low strain rate conditions of 0.01-1 s^-1（except 1 s^-1 at 1123 K） , softening effect is mainly due to dynamic recovery, while in high strain rate conditions of 1-10 s^-1 （include 1 s^-1 at 1123 K） due to dynamic recrystallization. Flow stress data was processed through the means of work-harden rate. Combined the inflection point criterion of Inθ-ε curves with the zero point criterions of ^2（1nθ）/ ε^2εcurves, critical conditions were researched. Results indicate that dynamic recrystallization during hot deformation occurs. Increase of strain rate and decrease of deformation temperature can inhibit occurrence of dynamic recrystallization. A critical stain model representing DRX critical conditions was further adopted and the mathematical relation between critical strain and thermodynamic parameters was exploited. Final simulation results show that the critical model is of high precision and the maximal relative error is less than 7.8%.