短切碳纤维/AZ91D镁合金复合材料高温变形动态再结晶行为

摘要

The dynamic recrystallization behavior of short carbon fiber(CFs)/AZ91D composite and AZ91D Mg alloy was investigated by isothermal compressive experiment at the deformation temperatures from 340℃ to 400℃, strain rates from 0.001 s-1to 1 s-1and a maximum true strain of 0.7.The results show that both CFs/AZ91D composites and Mg alloy exhibit an obvious dynamic recrystallization during being compressed at elevated tempera-ture.The addition of CFsgreatly promotes the dynamic recrystallization of the matrix alloy in the composite.As a result,the critical strain for dynamic recrystallization is reduced and a finer recrystallized grain structure is obtained in the composite.For the Mg alloy,the variation of volume fraction of dynamic recrystallization with the strain pres-ents the classical "S"mode.For the CFs/AZ91D composites,however,the increase of volume fraction of dynamic recrystallization with the increase of strain exhibits a rapid-slow-stable behavior.The dynamic recrystallization criti-cal strain and kinetics models of CFs/AZ91D composite and Mg alloy were developed according to the experimental results.Based on these models,the difference of the dynamic recrystallization behavior between CFs/AZ91D com-posite and Mg alloy was analyzed.%在变形温度为340~400℃、应变速率为0.001~0.1 s-1、最大真应变为0.7 的条件下,采用等温压缩实验研究了短切碳纤维(CFs)/AZ91D复合材料和 AZ91D镁合金的动态再结晶行为.结果表明:CFs/AZ91D 复合材料和 AZ91D镁合金在高温压缩过程中均发生了显著的动态再结晶;CFs极大地促进了 AZ91D基体的动态再结晶过程,减小了动态再结晶临界应变并细化了再结晶晶粒组织;AZ91D 镁合金动态再结晶体积分数随应变量增加表现为典型的"S"型变化曲线,而CFs/AZ91D复合材料则呈现出快速增长-缓慢增长-趋于平稳的非线性变化规律.根据实验结果分别建立了CFs/AZ91D复合材料和 AZ91D镁合金的动态再结晶临界应变模型和动力学模型,在此基础上分析了二者高温变形动态再结晶行为的差异.