时效消除AZ80镁合金的屈服不对称性

摘要

Samples of AZ80 alloy were hot extruded at 380 °C and aged at temperatures of 170 °C and 310 °C respectively for different periods to compare the effect of precipitate structures on the tensile-compressive yielding asymmetry in magnesium alloy. Uniaxial tension and compression along the extruded direction were carried out at room temperature. It was found that the yielding asymmetry in the aged samples was not as significant as that in the as-extruded samples. This was because twinning occurred less readily in the aged samples. And it was also confirmed by the fact that the increment of the critical resolved shear stress (CRSS) for twinning was higher and the Schmid factor was lower in the aged samples in the presence of precipitate. Thus, it was concluded that the yielding asymmetry could be reduced and even eliminated by increasing the area fraction of the precipitate phase.%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。