应变速度对等通道转角变形纯铝组织细化的影响

Influence of strain rate on microstructure of pure aluminum in the process of equal channel angular pressing

采用透射电镜和背散射电子衍射(EBSD)分析,观测了高纯铝在等通道转角变形加工(ECAP)中,三种应变速度对高纯铝显微组织的作用。结果表明:高速应变(100mm/s)可以进一步提高纯铝的硬度,使晶粒达到0.31μm;大角晶界的百分数增大,最高可达89%。对目前ECAP研究中出现的两个问题,进行了分析讨论。最后指出:强塑性形变后获得的具有大角晶界的超细等轴晶粒不是再结晶组织,因为它们的晶界位错密度很高,处在高能状态;这种组织是通过动态回复,而不是动态再结晶产生的。

The effect of strain rates used in the process of equal channel angular pressing（ECAP） on mierostrueture of pure aluminum was studied by transmission electron microscopy （TEM） and electron back-scattered diffraction （EBSD） analysis. The results show that high rate strain （100mm/s） can enhance hardness of the pressed A1, its grain size is refined to 0.31μm, and the fraction of high angle grain boundary in the pressed A/increases to 89%. It is found that ultra-fine equiaxed grains with high ang/e boundaries are not a recrystallized structure because dislocation density of their grain boundary is very high and lies in a high energy state, and the microstructure is formed by dynamic recovery, and not dynamic reerystallisation.