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通过AZ31B镁合金板材高温拉伸实验,分别讨论了成形温度、应变速率以及各向异性对镁合金流变的影响。实验结果表明,温度越高、应变速率越低,镁合金的塑性越好;取样方向与轧制方向成45°时,由于在此方位孪生取向因子最大,因而该方向的塑性很高,与0°方向塑性基本相同。对变形后的镁合金进行金相组织观察发现,250℃时镁合金显微组织几乎都是由细小的等轴晶粒组成,优于其他温度下的显微组织;结合温度对镁合金流变的影响,确定镁合金的最佳温成形温度为250℃。依据实验数据建立了两种硬化本构模型,即Fields-Backofen模型和指数模型。分别将两种模型预测结果与实验数据对比表明,采用指数模型能更好的预测镁合金温成形流变应力。
The effects of forming temperature, strain rate and anisotropy on the rheological behavior of magnesium alloy were discussed through high temperature tensile test of AZ31B magnesium alloy sheet. The experimental results show that the higher the temperature, the lower the strain rate, the better the plasticity of the magnesium alloy. When the sampling direction is at 45 ° to the rolling direction, the plasticity in this direction is very high due to the largest twin orientation factor in this direction, ° plastic direction is basically the same. The deformation of the magnesium alloy microstructure observation found that at 250 ℃, the microstructure of magnesium alloys are almost composed of fine equiaxed grains, better than the microstructure at other temperatures; combined temperature of the magnesium alloy rheological The best hot forming temperature of magnesium alloy is 250 ℃. Based on the experimental data, two kinds of hardening constitutive models, Fields-Backofen model and exponential model, were established. Comparing the prediction results of the two models with the experimental data respectively shows that the exponential model can predict the hot forming flow stress of magnesium alloy better.