Yu Xia, Wanlin Guo

International Journal of Fatigue   ，2026，109530

Abstract: Additively manufactured (AM) Ti-6Al-4V alloys often exhibit poor fatigue quality due to the presence of inherent defects, posing a major challenge for their widespread engineering application. Here, we developed a fatigue quality assessment approach based on three-dimensional fatigue fracture method, by a unified correlation between the Stress-Life (S-N) and fatigue crack growth properties of AM materials. It has been shown that the predicted probabilistic S-N curves derived from the actual defect size distribution capture the experimental fatigue life data within their scatter. The equivalent initial flaw size distribution of AM Ti-6Al-4V was back-extrapolated from S-N data, showing a reasonable correspondence, particularly in terms of magnitude, with the defect sizes observed at the fracture origins. It was further found that the fatigue crack growth behavior shows a weak dependence on the defect population, indicating that the fatigue quality of AM materials can be directly evaluated from their intrinsic defect quality. This provides a practical basis for optimizing AM process parameters with fatigue quality as the design target. As a demonstration, the proposed approach was further applied to evaluate the fatigue quality of Ti-6Al-4V alloys produced by additive manufacturing, conventional forging, and powder metallurgy routes, showing a reasonable agreement with experimental trends.

Link: https://www.sciencedirect.com/science/article/pii/S0142112326000502