Fatigue Crack Initiation and Growth Behaviors of Additively Manufactured Ti-6AI-4V Alloy After Hot Isostatic Pressing Post-Process

In this study, the fatigue crack initiation and growth behaviors of an additively manufactured (AM) Ti-6AI-4V alloy were investigated, and its prospect for fatigue applications was evaluated. The AM specimens were first fabricated by selective laser melting (SLM) and then underwent a cycle of annealing at 800 °C for 2 h and hot isostatic pressing (HIP) treatment at 920 °C/150 MPa/3 h followed by surface machining. Prefabricated spherical defects with different diameters (1.0 mm and 2.0 mm) were introduced to examine the efficacy of HIP treatment for eliminating the built defects. Both fracture morphology and microstructure were characterized to reveal the failure mechanism of these tested specimens. The results suggest that both the fatigue lives and fatigue crack growth resistances of most SLM+HIP-processed specimens are much higher than those of traditional wrought material, thus highlighting that the AM Ti-6AI-4V alloy can be a better candidate for future fatigue applications. However, due to the large variability in fatigue performance, the current SLM+HIP-processed Ti-6Al-4V alloy still cannot meet the demand for high safety and reliability.