The fatigue limit of Ti-6A1-2Zr-2Sn-3Mo-1Cr-2Nb titanium alloy with different colony features

The fatigue limit is a particularly important parameter when designing aerospace components. In this study, the fatigue limit of Ti-6A1-2Zr-2Sn-3Mo-1Cr-2Nb alloy with different colony features are studied. Three double annealing processes were conducted to prepare different colony microstructures. The results show that the colony microstructure with high yield strength does not necessarily get high fatigue limit, and even shows an reverse trend. It is due to that not only the yield strength but also the crack initiation mechanism of the fatigue specimen can exert influence on the fatigue limit of Ti-6A1-2Zr-2Sn-3Mo-1Cr-2Nb alloy. Generally speaking, the microstructure with small colonies and thick α platelets gets relatively low yield strength. However, it can obtain superior crack initiation resistance offered by crack initiation mechanism as well. Based on above findings, a fatigue limit prediction model is built. It is verified that the model can fairly predict the fatigue limit of Ti-6A1-2Zr-2Sn-3Mo-1Cr-2Nb alloy with colony microstructure.