Effect of homogenization annealing on internal residual stress distribution and texture in ME21 magnesium alloy extruded plates

The distribution of residual stresses through thickness of 5 mm-thick ME21 magnesium alloy extruded plates was analyzed non-destructively using short-wavelength X-ray diffraction(SWXRD),and the effect of homogenization annealing before extrusion on the residual stress was discussed.The classic d 0 method with an annealed stress-free reference specimen was employed to determine the residual stress of the extruded plates.The residual stress results showed that the gradient of residual stress in the transverse direction was larger than that of the extrusion direction.The homogenization process prior to extrusion weaken the formed sample’s texture.The maximum residual stress of the as-extruded plate was reduced,and the residual stress distribution was homogenized.

基于热扭转试验的ME21镁合金热变形行为研究

采用热扭转试验机对ME21镁合金在300～450℃、等效应变速率0．0100—0．0001s。范围内进行扭转试验，研究合金的热变形行为，利用Zener—Hollomon参数法通过数学分析构建了ME2。1合金基于热扭转试验的高温塑性变形的本构方程。结果表明：ME21镁合金在扭转温度450℃，等效应变速率0．01s^-1时，合金在断裂前的扭转圈数可以达到2．5圈，等效应变可达到1．1以上，在此种工艺下可以获得较高的热加工塑性。ME21镁合金在不同温度和不同应变速率下的热扭转过程中，硬化与软化的同时作用使得其流变过程的应力一应变曲线差异较大，扭转变形后均可得到再结晶组织，但是组织的差异也较大，再结晶晶粒尺寸取决于温度补偿应变速率参数Z的大小。合金本构方程为σ=1/0.03159ln{Z/1.547×10^6）1/2.4302＋[（Z/1.547×10^6）2/2.4302＋1]1/2｜，以此计算的流变应力的预测值与试验值相对误差平均值小于5％。ME21合金热扭转的变形激活能为Q=117．34kJ·mol^-1。

含稀土镁合金的热拉伸变形行为及性能研究

本文在结合镁合金常用塑性加工工艺基础上,采用Gleeble-1500D热模拟机,在温度分别为573K、633K、693K,应变速率在0.05～10.8s-1之间的条件下,对ME21镁合金进行高温快速拉伸试验。结果表明:合金的稳态流变应力随温度的升高而降低,随应变速率的增大而增大。同一应变速率下,峰值应力随温度的增高而出现得更晚。从应力应变曲线上也能反映合金在变形阶段产生了动态再结晶。在试验条件范围内合金的高温拉伸性能强度随变形温度的升高而减小,伸长率随变形温度的升高而增大。