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AZ80镁合金在380°C挤压之后,分别在170°C和310°C下进行不同时间的时效,以比较析出相的形貌和结构对镁合金屈服不对称性的影响。对沿挤压方向切取的样品在室温下进行单轴拉伸及压缩实验。结果发现,时效样品的拉压屈服不对称显然比未时效挤压样品的弱很多,这是因为时效样品中的孪生发生远少于挤压样品中的。此现象可以通过时效样品中孪生的临界剪切力增量比基面滑移的增量大,而其取向因子却减小使得其发生更困难来证实。镁合金中的拉压屈服不对称性可以通过增加析出相分数来减弱甚至消除。实验结果显示,当合金内析出相分数达到饱和后,拉压不对称性消失。
AZ80 magnesium alloy at 380 ° C after extrusion, respectively, at 170 ° C and 310 ° C under different aging time to compare the precipitated phase morphology and structure of magnesium alloy yield asymmetry. Samples taken along the direction of extrusion were uniaxially stretched and compressed at room temperature. As a result, it was found that the tension-compression yielding asymmetry of the aged samples is clearly much weaker than that of the non-aged samples because the occurrence of twins in the aged samples is much less than in the extruded samples. This phenomenon can be confirmed by the increase of the critical shear increment of the twin in the aged sample compared to the increment of the basal plane slip while the decrease of its orientation factor makes its occurrence more difficult. Tensile yield stress asymmetry in magnesium alloys can be reduced or even eliminated by increasing the fraction of precipitated phases. The experimental results show that when the phase fraction of the alloy reaches saturation, the tension and pressure asymmetry disappears.