材料科学
断裂韧性
共晶体系
极限抗拉强度
合金
电子背散射衍射
扫描电子显微镜
复合材料
韧性
拉伸试验
冶金
断裂力学
微观结构
作者
Zhenzhou Ji,Xiaoguang Qiao,Shoufu Guan,Jian Hou,Chengchen Hu,Fuguan Cong,Guojun Wang,M.Y. Zheng
出处
期刊:Crystals
[MDPI AG]
日期:2023-08-18
卷期号:13 (8): 1277-1277
标识
DOI:10.3390/cryst13081277
摘要
Low fracture toughness has been a major barrier for the structural applications of cast Mg-Gd-Y-Zr alloys. In this work, the tensile properties and fracture toughness of a direct-chill-cast Mg-9Gd-4Y-0.5Zr (VW94K) alloy were investigated in different conditions, including its as-cast and as-homogenized states. The results show that the tensile properties of the as-cast VW94K alloy are greatly improved after the homogenization treatment due to the strengthening of the solid solution. The plane strain fracture toughness values KIc of the as-cast and as-homogenized VW94K alloys are 10.6 ± 0.5 and 13.8 ± 0.6 MPa·m1/2, respectively, i.e., an improvement of 30.2% in KIc is achieved via the dissolution of the Mg24(Gd, Y)5 eutectic phases. The initiation and propagation of microcracks in an interrupted fracture test are observed via an optical microscope (OM) and scanning electron microscope (SEM). The fracture surfaces of the failed samples after the fracture toughness tests are examined via an SEM. The electron backscatter diffraction (EBSD) technique is adopted to determine the failure mechanism. The results show that the microcracks are initiated and propagated across the Mg24(Gd, Y)5 eutectic compounds in the as-cast VW94K alloy. The propagation of the main cracks exhibits an intergranular fracture pattern and the whole crack propagation path displays a zigzag style. The microcracks in the as-homogenized alloy are initiated and propagated along the basal plane of the grains. The main crack in the as-homogenized alloy shows a more tortuous fracture characteristic and a trans-granular crack propagation behavior, leading to the improvement of the fracture toughness.
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