Effect of Alpha Phase Characteristics on the High Cycle Fatigue Properties of Ti-6Al-4V Alloy

In this paper, high cycle fatigue (HCF) properties of Ti-6Al-4V alloys prepared by different forging processes have been investigated. Optical microscopy (OM) and Transmission electron microscopy (TEM) were used to characterize microstructure, and the fatigue fracture micromechanisms were analyzed. Fracture surfaces of specimens were observed by scanning electron microscopy (SEM) to identify the macroscopic fracture mode. It was found that die forging at high temperature would increase the proportion of low angle grain boundary in equiaxed primary α phase and lead to lamella secondary α coarsen with the appearance of dislocation networks, which would make the HCF properties decline. Besides, it showed that the HCF properties increase with increasing the volume fraction of primary α.