High cycle fatigue and fatigue crack propagation behaviors of β-annealed Ti-6Al-4V alloy

The effect of β annealing on high cycle fatigue (HCF) and fatigue crack propagation (FCP) behaviors of Ti64 alloy were examined, and the results were compared to those of mill-annealed counterpart. The tensile tests, stress-controlled HCF tests, and FCP tests were conducted, and the fractographic and micrographic analyses were performed before and after the tests. The β-annealed Ti64 specimen showed inferior HCF properties as compared to the mill-annealed counterpart, as a result of lower yield strength. On the other hand the resistance to FCP of β-annealed Ti64 specimen was higher than that of mill-annealed counterpart in low and intermediate ΔK regime. Relatively easy fatigue crack initiation at the colony boundaries of β-annealed Ti64 specimen reduce the resistance to HCF. The resistance to FCP of β-annealed Ti64 specimen increased significantly particularly in low ΔK regime along with severe crack branching and deflection.