Jiang Haiyang, Zhang Jianyang, Xie Bijun, He Zhangxun, Zhang Hao, Wang Bing, Xu Bin, Wu Yuxi, Sun Mingyue
Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
School of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
Materials (Basel). 2020 Sep 29;13(19):4332. doi: 10.3390/ma13194332.
The impact toughness of a TA31 titanium alloy cylindrical shell was investigated systemically after ring rolling. The impact toughness of specimens with different notch orientations shows obvious anisotropy. The microstructure of the cylindrical shell and the impact fracture were characterized by an optical microscope and scanning electron microscope. The results show that cracks are easier to propagate in the equiaxed α phase than the elongated α phase. This is because the expanding cracking path in the equiaxed α phase is shorter than that in the elongated α phase, and thereby the cracks are easier to propagate in the equiaxed α phase than the elongated α phase. More specifically, the α phase on the RD-TD plane was obviously isotropic, which makes it easy for the cracks to propagate along α grains in the same direction. However, the α phase on the RD-ND plane has a layered characteristic, and the direction of the α phase varies from layer to layer, thus it requires higher energy for cracks to propagate across this layered α phase. Therefore, the cracks propagating in the same α phase orientation take easier than that in the layered α phase, so it has lower impact toughness.
对TA31钛合金圆柱壳环轧后的冲击韧性进行了系统研究。不同缺口取向试样的冲击韧性表现出明显的各向异性。采用光学显微镜和扫描电子显微镜对圆柱壳的微观组织和冲击断口进行了表征。结果表明，裂纹在等轴α相中比在拉长α相中更容易扩展。这是因为等轴α相中裂纹扩展路径的延伸比拉长α相中短，从而裂纹在等轴α相中比在拉长α相中更容易扩展。具体而言，RD-TD平面上的α相明显各向同性，这使得裂纹易于沿α晶粒在同一方向扩展。然而，RD-ND平面上的α相具有层状特征，且α相的方向层间各异，因此裂纹穿过这种层状α相扩展需要更高的能量。所以，裂纹在相同α相取向中扩展比在层状α相中更容易，其冲击韧性较低。
