7075-T6铝合金在Taylor冲击实验中的宏观力学响应及细观结构演化

Macroscopic Mechanical Response and Microstructure Evolution of 7075-T6 Aluminum Alloy in Taylor Impact Test

将实验和晶体塑性有限元(CPFEM)方法相结合,研究了7075-T6铝合金在Taylor冲击实验中的宏观力学响应以及其细观结构的演化。使用电子背散射衍射技术(EBSD)对实验前7075-T6铝合金的细观结构进行表征。通过修改强化模型和流动准则在CPFEM模型中引入位错密度作为内部状态变量,并结合动态压缩实验得到的应力-应变曲线确定7075-T6铝合金相关的模型参数。结果表明:考虑位错密度的CPFEM模型可有效地描述7075-T6铝合金在不同速度Taylor冲击实验中的宏观和微观力学响应。与实验结果对比,CPFEM模型合理地预测了冲击后子弹的外部轮廓变化,其预测的撞击面半径和子弹剩余长度与实验结果误差均在10%以内。此外,CPFEM模型预测7075-T6铝合金冲击后的织构演化同动态冲击后结果大致相同,均表现为生成了较多的R-Cube织构和Goss织构,而Cube织构和Cu织构大量减少。随着冲击速度的增加,R-Cube织构、S织构的体积分数逐渐增大,Cube织构、Cu织构和Brass的体积分数逐渐减少。同时,CPFEM模型预测到撞击后子弹颈缩段的产生。随着冲击速度的增加,子弹的对数应变和位错密度均有上升,最大值均出现在撞击面;在同一速度下,撞击面上外表面处平均位错密度的值小于轴心处的值。

Macroscopic mechanical responses,microstructure evolution of 7075-T6 aluminum alloy during deformation under Taylor impact test were investigated by experiments and crystal plasticity finite element method.The microstructure of 7075-T6 aluminum alloy before the test was characterized by electron back scattering diffraction technique(EBSD).The internal state variables of dislocation density were introduced into CPFEM model by modifying the strengthening model and flow criterion,and the 7075-T6 aluminum alloy related model parameters were determined by combining the stress-strain curves of the dynamic compression test.The results show that the CPFEM model considering the dislocation density can effectively describe the macroscopic and microscopic mechanical responses of 7075-T6 aluminum alloy.Compared with that of the experimental results,the CPFEM model can reasonably predict the geometrical changes of cylinder after impact,and the relative errors of the predicted impact face radius and the remaining length of cylinder are within 10%of the experimental results.In addition,the CPFEM model predicts that the texture evolution of 7075-T6 aluminum alloy after impact is roughly the same as that after dynamic impacting,which shows that there are more R-Cube texture and Goss texture,while Cube texture and Cu texture decrease greatly.Meanwhile,the CPFEM model predicted there is necking in cylinder after impact;with the increase of velocity,the values of logarithmic strain and dislocation density of cylinder also increase,and the maximum value appears at the impact face.At the same velocity,the average dislocation density of the external surface is less than that of the axial at the impact face.