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Compressive deformation and fracture behaviors of AZ31 magnesium alloys with equiaxed grains or bimodal grains
Materials Science and Engineering: A ( IF 6.4 ) Pub Date : 2018-05-23 , DOI: 10.1016/j.msea.2018.05.081
Xinfeng Li , Jin Zhang , Dewen Hou , Qizhen Li

The compressive mechanical properties, microstructural evolution and fracture behaviors of AZ31 alloys with equiaxed grains (E-grain) or bimodal grains (B-grain) were investigated using optical microscopy, scanning electron microscopy and electron backscattered diffraction. The results indicate that the ratio of twinned grains to all grains increases for both E-grain and B-grain samples with increasing strain levels during compression deformation along the extruded direction. The average Schmid factor for {10–12} twins of B-grain samples is higher than that of E-grain samples, which lowers required activating stress for {10–12} twins in B-grain samples. This causes a higher quantity of twins in B-grain samples than that of E-grain samples at the same pre-compression level. The E-grain samples mainly exhibit parallel twins regardless of pre-compression levels, whereas the twins in coarse grains of B-grain samples are parallel to each other at low compressive strain level and then transform to crossed twins at high compressive strain level with parallel twins in fine grains. Additionally, the peak strength, strain hardening rate and fracture strain of E-grain samples are lower than those of B-grain samples, and they possess similar yield strength. The coarse grains in the B-grain samples effectively resist crack growth by deflecting and branching crack tips, bridging of the cracks and forming the secondary cracks. Meanwhile, the fine grains in B-grain samples accommodate plastic strain and mediate multiple grains’ deformation. The concurrent effect of coarse grains and fine grains results in the improvement of plasticity.



中文翻译:

等轴晶粒或双峰晶粒的AZ31镁合金的压缩变形和断裂行为

利用光学显微镜,扫描电子显微镜和电子背散射衍射研究了具有等轴晶粒(E晶粒)或双峰晶粒(B晶粒)的AZ31合金的压缩力学性能,显微组织演变和断裂行为。结果表明,在沿挤压方向压缩变形期间,E晶粒和B晶粒样品的孪晶晶粒与所有晶粒的比率均随应变水平的增加而增加。B谷物样品的{10-12}双胞胎的平均Schmid因子高于E谷物样品,这降低了B谷物样品的{10-12}孪生的所需激活应力。在相同的预压缩水平下,这导致B粒样品中的双胞胎数量高于E粒样品中的双胞胎数量。不论预压缩水平如何,E颗粒样品主要表现出平行孪晶,而B颗粒样品的粗粒中的孪晶在低压缩应变水平下彼此平行,然后在高压缩应变水平下平行转变为交叉孪晶。双胞胎在细小颗粒。另外,E晶粒样品的峰值强度,应变硬化速率和断裂应变低于B晶粒样品的峰值强度,应变硬化速率和断裂应变,并且它们具有相似的屈服强度。B晶粒样品中的粗晶粒通过偏转和分支裂纹尖端,桥接裂纹并形成次生裂纹,有效地抵抗了裂纹的增长。同时,B晶粒样品中的细晶粒可承受塑性应变并介导多个晶粒的变形。

更新日期:2018-05-23
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