论文部分内容阅读
对经受过不同的热机械加工并在恒幅疲劳试验中断裂的两种钛合金(Ti-6-4和Ti-6-6-2)的试样作了断口金相检验。结果表明,合金的化学成份与断裂方式之间没有明确的相应关系。然而,却发现局部裂纹发展与清晰的显微组织有依赖关系。α-晶粒边界和α-β交界面被所出现的二次裂纹显露出来,表明了这些部位较弱。同时,在裂纹生长率较低的范围内,观察不到疲劳条纹;但是在裂纹生长率较高的情况下,断口外观以疲劳条纹为主,快速断裂区以珠状波纹断裂为主。这些合金的断裂,可用正好在生长着疲劳裂纹前面的局部周期性加工硬化区来加以解释。
Fracture metallurgical tests were performed on two samples of titanium alloys (Ti-6-4 and Ti-6-6-2) that had undergone different thermomechanical processing and were fractured in a constant amplitude fatigue test. The results show that the chemical composition of the alloy and the fracture mode does not have a clear corresponding relationship between. However, it has been found that the development of localized cracks has a dependency on clear microstructure. The appearance of secondary cracks in the α-grain boundaries and the α-β interface revealed that these sites were weaker. At the same time, no fatigue streaks were observed in the range of lower crack growth rate. However, in the case of high crack growth rate, the appearance of the fracture was mainly in the form of fatigue streaks, and the rapid fracture zone was dominated by the bead-like moire fracture. The fracture of these alloys can be explained by the locally periodic work-harden zone just before the fatigue crack growth.