NiCoFeCrAl系高熵合金热加工图不同失稳判据比较

Comparison of Different Instability Criteria for Processing Maps of NiCoFeCrAl High Entropy Alloy

摘要:

采用Gleeble-3800热模拟试验机对NiCoFeCrAl系高熵合金进行单道次热压缩实验研究，根据峰值应力构建了NiCoFeCrAl系高熵合金Arrhenius本构关系模型，运用Prasad、Murty、Gegel和Malas四种失稳准则，构建了不同失稳判据下的DMM热加工图，并对不同失稳判据在该合金热变形过程中的适用范围进行了分析与比较，确定了该合金的最佳热加工区间为温度为980~1010 ℃+应变速率为0.01~0.001 s^-1和温度范围为1050~1100 ℃+应变速率为0.01~0.1 s^-1，平均功率耗散率大于36%。借助EBSD显微组织分析，确定了热变形的软化机制随变形量的增大由动态回复向动态再结晶转变。

Abstract:

The single-pass thermal compression experiments were conducted on NiCoFeCrAl high entropy alloy by Gleeble-3800 thermal simulation tester. The Arrhenius constitutive model was established based on the peak stresses. With four instability criteria (Prasad, Murty, Gegel, and Malas), different heat processing maps of dynamic material model were established. The applicable ranges of the instability criteria for the alloys in the heat deformation process were analyzed and compared. Results show that the optimal heat processing ranges of the alloys are the temperature range of 980–1010 °C+strain rate of 0.01–0.001 s^-1 and the temperature range of 1050–1100 °C+strain rate of 0.01–0.1 s^-1. The average power dissipation rate is greater than 36%. Through EBSD microstructure analysis, the softening mechanism of thermal deformation is changed from dynamic recovery to dynamic recrystallization with increasing the deformation amount.