耦合位错密度的6111铝合金热变形本构模型

Constitutive model coupled with dislocation density for hot deformation of 6111 aluminum alloy

利用Gleeble-1500热模拟试验机对6111铝合金进行高温拉伸试验,研究了其在变形温度为350、450和550℃以及应变速率为0.1、1和10 s 1时的热变形行为.6111铝合金的流变应力随温度升高而减小,随应变速率增大而增大,其热变形从应变硬化阶段过渡到稳态变形阶段.建立了综合考虑应变、温度和应变速率对流变应力的影响以及耦合位错密度的统一黏塑性本构模型,并通过遗传优化算法求解出本构模型中的材料常数.模型计算得到的真应力-真应变曲线与试验数据吻合较好.

The hot deformation behavior of 6111 aluminum alloy was investigated by high-temperature tensile testing on a Gleeble-1500 thermal-mechanical simulator at deformation temperatures of 350, 450, 550 ℃ and strain rate of 0.1, 1, 10 s-1. It is shown that the flow stress of the aluminum alloy decreases when the temperature rises but increases when the strain rate increases, and the hot deformation behavior transfers from a strain-hardening deformation stage to a steady-state deformation stage. A unified viscoplastic constitutive model coupled with dislocation density was established in consideration of the effects of strain, temperature and strain rate on the flow stress. Material constants in the constitutive model were solved through a genetic algorithm. Predicted true stress-true strain curves calculated by this model are in good agreement with experimental data.