AZ31镁合金方管挤压成型的数值模拟

Numerical Simulation of Square Tube Extrusion for AZ31 Magnesium Alloys

基于AZ31镁合金热压缩真应力-真应变曲线,计算得到了流变应力方程,分析了合金压缩变形后的显微组织,并用HyperXtrude有限元分析软件对AZ31镁合金方管挤压成型进行了数值模拟,最后进行了试验验证。结果表明:AZ31镁合金的流变应力随变形温度的升高而减小,并在350℃以上较快达到稳态,易于加工成型;热压缩变形后合金中的孪晶组织随温度的升高有所减少,且晶粒不断长大,在高应变速率时由于动态再结晶不充分,晶界附近形成类似"项链"状的细小晶粒组织;有限元模拟分析发现方管角部金属流速低于中心位置,在HyperStudy中经工作带优化后流速分布均匀,采用优化设计的模具挤压生产出了合格的AZ31镁合金型材。

On the basis of true flow stress-true strain curves of AZ31 magnesium alloys obtained from hot compression process, the corresponding flow stress equation was presented and the microstructure of the compressed alloy was analyzed.The square tube extrusion process for AZ31 magnesium alloy was simulated by using the HyperXtrude software.The results show that the flow stress decreased with the increasing temperature and could reach the steady state quickly above 350 ℃,which is suitable for processing forming.The twins in hot compression specimens reduced with the temperature increasing,moreover the grains were growing up.With the high strain rate,the fine grains similar to “necklace”appeared on the grain boundaries due to the insufficiency of dynamic recrystallization.The finite element simulation results show that the metal velocity in the corner of the square tube was lower than that in the center,but could distribute well as the optimization of the bearing part in the HyperStudy.The die designed on the optimized die bearing model proved to be capable of producing the qualified products in practice.