压下模式对镁合金宏观塑性变形和微观组织演变的影响

Effects of Compressive Mode on Macroscopic Deformation and Microstructure Evolution of Magnesium Alloy

将热-力耦合弹塑性有限元方法与微观组织演化模型相集成,定量比较了恒定平均应变速率和恒定压头速率2种压下模式对镁合金AZ31B高温变形和微观组织演变的影响.采用AZ31B镁合金圆柱形试样进行Gleeble热力模拟试验获得有限元模拟所需的高温流动应力曲线与再结晶晶粒尺寸实测数据,并通过二次开发与有限元模型相集成.研究结果表明,由于端面摩擦的存在,2种压下模式下变形场和微观组织场都呈现不均匀分布特性.与恒定平均应变速率相比,恒定压头速率压下时晶粒尺寸均值减小,均方差略有增加.

A microstructural evolution model was integrated with a thermal-mechanical elastic-plastic finite element method to quantitatively simulate the hot deformation and microstructural evolution of magnesium alloy AZ31B at two different compressive modes, constant strain rate and constant die velocity. The stress- strain curves and recrystallized grain sizes were obtained from hot compressive deformation of AZ3lB on Gleeble-1500 thermo-simulation machine and integrated with the finite element model through the user subroutine interface. It is shown that the fields of deformation and microstructure are non-uniformly dis- tributed as a result of the existence of friction. Compared with the sample compressed at a constant strain rate, the mean value of the grain size decreases and the mean square error increases slightly for the sample at a constant die velocity.