The microstructure and high temperature properties of the AXE622 Mg alloy were investigated after the conventional and semisolid casting processes. The tensile test was conducted at room temperature, and 473 K. Impression creep test was performed at a temperature range of 423–498 K under the stress range of 450–600 MPa. The microstructure of the conventional and semisolid alloys contains α-Mg dendrites, the eutectic phase, secondary phases including (Mg–Al)₂Ca, eutectic Mg₁₇Al₁₂, and Al₁₁RE₃. During semisolid processing, coarse dendrites of the α-Mg became fine, globular, and Rosetta shape. The average length of the secondary phases in the semisolid alloy decreased from 4.21 to 2 μm and the average grain size of the α-Mg reduced from 113 to 96 μm. Semisolid processing caused a significant improvement in the tensile and creep resistance of the AXE622 Mg alloy. The stress exponent for creep was calculated in the range 5.6–7.7 for the conventional alloy and in the range 10.3–11 for the semisolid alloy. The activation energy for conventional and semisolid alloy was determined as 71.4 kJ/mol and 78.3 kJ/mol, respectively. It was concluded that the dominant creep mechanism in the conventional alloy was the grain boundary diffusion-controlled dislocation climb, while in the semisolid alloy was the power-law breakdown.

Graphic Abstract

中文翻译：

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AXE622铸造Mg合金的组织与高温力学行为。

在常规和半固态铸造工艺之后，研究了AXE622 Mg合金的组织和高温性能。拉伸试验是在室温和473 K下进行的。压缩蠕变试验是在423-498 K的温度范围内，应力范围为450-600 MPa的条件下进行的。常规和半固态合金的微观结构包含α-Mg树枝晶，共晶相，包括（Mg–Al）₂ Ca的次级相，共晶Mg ₁₇ Al ₁₂和Al ₁₁ RE ₃。在半固体加工过程中，α-Mg的粗枝晶变成细小，球形和罗塞塔形状。半固态合金中第二相的平均长度从4.21减小到2μm，α-Mg的平均晶粒尺寸从113减小到96μm。半固态加工大大改善了AXE622 Mg合金的拉伸强度和抗蠕变性。计算得出，常规合金的蠕变应力指数在5.6–7.7范围内，半固态合金的蠕变应力指数在10.3–11范围内。常规合金和半固态合金的活化能分别确定为71.4 kJ / mol和78.3 kJ / mol。可以得出结论，常规合金的主要蠕变机理是晶界扩散控制的位错爬升，而半固态合金是幂律击穿。

图形摘要