Effect of Microstructure on High Cycle Fatigue and Fatigue Crack Propagation Behaviors of beta-Annealed Ti-6Al-4V Alloy

Abstract

High cycle fatigue (HCF) and fatigue crack propagation (FCP) behaviors of beta-annealed Ti64 alloys having a microstructure of either alpha colonies or basketweave were studied. It was found that the resistance to HCF of beta-annealed Ti64 alloys with a microstructure of alpha colonies was similar but slightly inferior to those with a microstructure of basketweave. On the other hand, the FCP rates of beta-annealed Ti64 alloys having a microstructure of alpha colonies were lower than those of basketweave, particularly in low Delta K regime. Crack path observation on the surfaces of beta-annealed Ti64 alloy specimens suggested that crystallographic crack growth prevailed in the microstructure of alpha colonies, leaving cleavage facets on the fracture surface and less fatigue damage at the tip of crack. Based on the fractographic and micrographic examination, the effects of microstructure on the HCF and FCP behaviors of beta-annealed Ti64 alloys were discussed. Graphic