7A85铝合金塑性变形过程位错密度模型

Dislocation density model of 7A85 aluminum alloy during plastic deformation process

通过等温热压缩试验,研究7A85铝合金在应变速率为0.001~0.5 s^−1、变形温度为250~450℃条件下的流变行为。结果表明,7A85铝合金在塑性变形过程中,流变应力达到峰值前后的软化机制不同。在流变应力达到峰值应力前,加工硬化作用占主导地位,软化机制主要是材料内部位错的交滑移,动态回复不明显。当流变应力达到峰值后,材料内部发生明显的动态回复和再结晶现象。基于流变应力达到峰值前后的软化机制不同,建立了“两阶段”式Kocks-Mecking(K-M)位错密度模型来描述7A85铝合金塑性变形过程的位错密度演变规律,并验证了模型的准确性。

The flow behavior of 7A85 aluminum alloy was studied by isothermal compression test at the strain rate range of 0.001−0.5 s^−1 and temperature range of 250−450℃.The results show that,during the plastic deformation process,the softening mechanism of the flow stress is different before and after the peak flow stress of the 7A85 aluminum alloy.Before the flow stress reaches the peak,the work hardening is dominant and the main softening mechanism is the cross-slip of the dislocation inside the material,whereas,the dynamic recovery is not obvious.After the flow stress reaches the peak,the obvious dynamic recovery and recrystallization occur inside the material.Based on the difference of the softening mechanism before and after the peak stress,a“Two-stage”Kocks-Mecking(K-M)dislocation density model was established to describe the dislocation evolution during the plastic deformation process of 7A85 aluminum alloy,and the accuracy of the model was verified.