多应变率下Ti-811钛合金针状组织压缩变形及断裂机制

The compressive deformation and fracture mechanism for the acicular microstructure of Ti-811 titanium alloy under different strain rates

摘要:

本文采用Instron力学实验机及分离式 Hopkinson 压杆系统,分别对Ti-811钛合金针状组织进行静、动态压缩实验,以研究其不同应变率下的变形及断裂机制。结果表明：随应变率升高,针状组织屈服强度依次呈现正-负-正的应变速率敏感性,其内在原因是位错滑移机制和孪生变形机制的相互竞争。针状组织在静态和动态加载下的断裂机制明显不同,分别呈现为双剪切及单剪切断裂模式。动态加载试样端面部位可形成连续锯齿型金属屑,这是由于高速变形过程中主剪切带两侧金属的剧烈错动被入射杆与透射杆遏制所导致。

Abstract:

The static and dynamic compression tests of Ti-811 alloy with acicular microstructure have been conducted by using the Instron testing machine and the split Hopkinson bar system respectively. Its deformation and fracture mechanism under various strain rates have been studied. The results show that: the yield strength of acicular microstructure exhibits positive-negative-positive strain rate sensitivity successively with increasing strain rate. The intrinsic reason is the competition between dislocation slip and twinning mechanism. The fracture mechanisms of acicular microstructure under static and dynamic compression are obviously different, which show double-shearing and single-shearing fracture mode respectively. Saw-tooth chips formed at the end faces of dynamic compression specimen, which is due to restraint of the severe relative slide of the material at the two sides of primary shearing band by incident bar and transmission bar.