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使用带有高角环形暗场探测器的扫描透射电镜研究了Mg-2.1Gd-1.1Y-0.82Zn-0.11Zr合金的铸态组织特征,确认了由晶界向晶内延伸的层片状结构为γ′相的集合体;研究了时效峰值态的Mg-2.1Gd-1.1Y-0.82Zn-0.11Zr合金在总应变控制下的高温(573 K)低周疲劳测试中的力学响应和失效机制。在573 K下,合金在不同的总应变幅控制的循环加载中均表现出了循环软化的特征。扫描电镜的观察结果表明:微观裂纹优先在长周期有序相和基体的界面处形核,并沿基面扩展;分布于晶界处的、块状长周期有序相能抑制裂纹的穿晶扩展。
The as-cast microstructure of Mg-2.1Gd-1.1Y-0.82Zn-0.11Zr alloy was investigated by scanning transmission electron microscopy with a high-angle circular dark field detector. It was confirmed that the lamellar structure extending from the grain boundary into the crystal was γ ’phase. The mechanical response and failure mechanism of the aging peak-aged Mg-2.1Gd-1.1Y-0.82Zn-0.11Zr alloy at low temperature (573 K) under the total strain control were studied. At 573 K, the alloys exhibited cyclic softening behavior under different cyclic loads controlled by the total strain amplitude. Scanning electron microscopy results show that: the micro-cracks preferentially nucleate at the interfaces of the long-period ordered phase and the matrix and extend along the basal planes; the distributed long-period ordered phases in the grain boundaries can inhibit the transgranular cracks Expand.