TC6钛合金动态压缩变形中“应力塌陷”的形成原因

采用分离式Hopkinson Bar技术和一种新型的中断动态试验方法对TC6钛合金进行了动态压缩试验,通过光学显微镜、扫描电子显微镜分析了TC6钛合金变形到不同应变量时所产生绝热剪切带的微观形貌,通过与宏观力学响应相对应,研究了TC6钛合金在动态压缩变形中,绝热剪切带的形成过程及造成应力快速下降的原因。结果表明:在高应变率下,材料绝热剪切带的形成是一个由萌生、扩展、完全发展组成的过程;在应变率为2.5×10~3s~(-1)的动态压缩过程中,"应力塌陷"现象是由于材料内产生了大于一定尺寸的微裂纹所致。

On the formation cause of stress collapse in TC6 alloy under dynamic compression

Using the technology of split Hopkinson bar and a new method that can be used to interrupt test and obtain different amount of strain, dynamic compression test has been done on TC6 titanium alloy. By associating microstructure of shear band under different amount of strain with mechanical response of material, the formation cause of stress collapse in TC6 alloy under dynamic compression has been studied. It is shown that formation of adiabatic shear band of materials under high strain rate is a process composed of initiation, expansion and full development, and that stress collapse in stress-strain curvy is not resulted from the initiation and growing of adiabatic shear band, even involving cracks with its size not larger than certain critical size. Real reason of stress collapse in curvy is due to size of cracks has exceeded certain size within the adiabatic shear band.