The Influence of Laser Shock Peening on the Behavior of Ti6Al4V Titanium Alloy Under Gigacycle Fatigue Conditions

ABSTRACT This study investigates the gigacycle fatigue behavior of Ti6Al4V titanium alloy—a critical aerospace material—following laser shock peening (LSP). Previous research conducted by the authors has shown that LSP can improve the fatigue life of samples with stress concentrations by as much as eight times; however, this study indicates a contradictory decline in fatigue performance under gigacycle conditions ( N = 10 10 ) when using ultrasonic testing (Shimadzu USF‐2000). In contrast to the established LSP benefits, the treated specimens exhibited a substantial decrease in the fatigue limit when compared to the as‐received material. Infrared thermography revealed significantly elevated levels of energy dissipation in LSP‐processed specimens, whereas fractography showed a complete transition in failure origin: cracks invariably initiated centrally in LSP specimens versus near‐surface initiation in untreated counterparts. These outcomes are attributed to tensile residual stresses in the specimen core and the microstructural alterations induced by LSP. The residual stresses are estimated by numerical simulation based on the Johnson–Cook and Fabbro models.