The Fatigue Deformation Mechanism of TC17 Alloy with Residual Stress and Microstructure Dual Gradients

Surface deformation strengthening treatment could effectively enhance the fatigue properties of aerospace titanium alloy components, which is attributed to the occurrence of residual compressive stress and microstructure dual gradients. However, the evolution of the dual gradients during fatigue deformation has barely been studied, and the deformation mechanism is still puzzling. In this work, TC17 alloys were strengthened by ultrasonic shot peening (USP) treatment. The fatigue life of USP-20W is 73% higher than that of the original alloy. During fatigue deformation, the dislocation density in the surface and subsurface layers is further increased to enhance work hardening, while the < 001 > _β//LD texture and < 111 > _β//LD texture rotate towards the < 112 > _β//LD texture for balancing strength and plasticity. Notably, the fatigue crack initiation site of USP-20W was located approximately 80 μm below the surface. It is attributed to the dislocation accumulation and local stress concentration caused by the orientation mutation of β-Ti, which favors the formation of a localized weak zone for fatigue damage. This finding holds substantial significance for optimizing material performance in aerospace components.