多向镦粗7075铝合金动态再结晶组织晶粒度预报

Prediction of dynamic recrystallized grain size of 7075 aluminum alloy prepared by multidirectional upsetting

采用多向镦粗对7075铝合金试样进行压缩,利用有限元软件对多向镦粗的组织晶粒度预报,探索模拟分析与实验分析相结合的方法,研究7075铝合金多向镦粗过程的组织晶粒变化规律,并对五道次镦粗试样与初始样进行室温拉伸力学性能测试和采用SEM断口形貌观察。模拟结果表明:经过5道次镦粗后试样中心区域的组织晶粒明显细化,晶粒尺寸从初始的40μm减小到17μm;随着道次的增加,组织晶粒细化效果逐渐减弱。对比模拟预报与实验分析结果表明:两者在晶粒细化程度上吻合良好;经过5道次镦粗之后,拉伸断裂强度从初始的547 MPa增加到665 MPa,断面收缩率从初始的7.1%增加到28.4%,断口韧窝深而大,强度塑性明显提高。

The process of multidirectional upsetting of 7075 aluminium alloy was numerically simulated using a finite element software to predict the recrystallized microstructure and grain size. The method of combination of finite element simulation and experiment was employed to investigate the variation of microstructure and grain size and tensile test at room temperature was carried out for the alloy upset for one pass to five passes. The simulation results show that the grain size in the central area reduces remarkably for the sample after five upsetting passes, which reduces from 40 tLm to 17 /xm. The effect of the grain refinement weakens gradually with the increasing of the pass number. The result of comparing the simulated value with the experimental observation demonstrates that a good agreament in grain refinement between the two is obtained and the tensile strength increases from 547 MPa to 665 MPa with the reduction of area increasing from 7.1% to 28.4% for the alloy after five upsetting passes,for which the deep and large dimples on the tensile fracture are observed,