Plastic Deformation of AZ31 Magnesium Alloy under Various Temperature Conditions
Plastic Deformation of AZ31 Magnesium Alloy under Various Temperature Conditions
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AZ31镁合金在不同温度条件下的塑性变形
DOI：
10.2472/jsms.57.688
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
N. Deguchi
中科院分区：
文献类型：
--
作者：
Takamasa Yoshikawa;M. Tokuda;T. Inaba;H. Iwasaki;Koichi Machino;N. Deguchi
通过不同温度条件下的多次加载试验和塑性变形后显微组织的观察，研究了AZ31镁合金挤压圆柱体的变形机制与温度条件和加载路径的关系。实验结果表明，AZ31镁合金在室温下按孪晶变形机制进行塑性变形。AZ31镁合金在室温下很难塑性变形，因为孪晶变形的临界剪应力远大于穿晶滑移的临界剪应力。因此，由于孪生变形机制，AZ31镁合金在室温下的屈服面与von Mose准则估计的屈服面不一致，压缩和扭转试验的屈服应力低于拉伸试验的屈服应力。从屈服面的形状和微观组织中孪晶的存在来看，423K时的变形机制与室温下的变形机制相似。673K时发生晶界滑移和细化的超塑性变形。然后，对于屈服面，压缩试验的屈服应力等于拉伸试验的屈服应力，剪切屈服应力占拉伸屈服应力的80%。在473K、498K和523K的温度下，出现了屈服面的形状，在523K的变形中观察到了晶粒的细化。因此，在这些温度条件下，晶界滑动机制对塑性变形的影响是明显的。由于AZ31镁合金在473K以上的温度下表现出晶界滑移机制和导致超塑性变形的晶粒细化，因此认为较低的温度有利于AZ31镁合金的塑性加工。
The deformation mechanism of the extruded cylinder of AZ31 magunesium alloy depending on a condition of temperature and loading path was studied by a multi-loading test under various temperature conditions and an observation of its microscopic structure after the plastic deformation. From the experimental results, AZ31 magnesium alloy is plastically deformed at room temperature by a twin deformation mechanism. AZ31 magnesium alloy is hard to be plastically deformed at room temperature because the critical shear stress of the twin deformation is much larger than that of a trans-granular slip. Thus, due to the twin deformation mechanism, the yield surface of AZ31 magnesium alloy at room temperature does not coincide with the surface estimated by von Mises criterion, and then the yield stresses of a compressive test and torsion test are lower than the yield stress of a tensile test. From the shape of the yield surface and the existence of the twin in microscopic structure, the deformation mechanism at 423K is similar to the mechanism at room temperature. The superplastic deformation driven by a grain boundary sliding and the grain refinement occurs at 673K. Then, concerning the yield surface, the yield stress of a compressive test is equal to that of a tensile test, and the shear yield stress shows 80% of the tensile yield stress. Such as a shape of the yield surface appears at the temperature of 473K, 498K and 523K and the grain refinement is observed in the specimen deformed at 523K. Therefore, at these temperature conditions, the influence of the grain boundary sliding mechanism appears on the plastic deformation. Because the grain boundary sliding mechanism and the grain refinement leading to the superplastic deformation reveal at a temperature more than 473K, it is supposed that the plastic work-ability of AZ31 magnesium alloy can be facilitated at a comparatively lower temperature.