Mechanical properties and strengthening mechanisms of Ti-6Al-4V treated by electro-pulsing assisted laser shock peening

Laser shock peening (LSP) is an efficient surface treatment method used to improve the mechanical properties of materials. With the growing demand for high-performance components under extreme conditions, there is a need for further improvement in the effects of LSP. Recently, electro-pulsing assisted laser shock peening (EP-LSP) has emerged as a promising technique to enhance the effects of single-mechanical-field LSP. However, there has been limited systematic research on the effects of mechanical properties and strengthening mechanisms of material treating by EP-LSP. Herein, Ti-6Al-4V samples were subjected to synchronous treatment with electro-pulsing and LSP. The effects of EP-LSP on surface and subsurface characteristics, including surface morphology, hardness, residual stress and microstructure, were investigated and compared with both as-received and LSP-treated samples. Furthermore, the strength and ductility properties were carefully analyzed, and the strengthening mechanism was elucidated. It was observed that EP-LSP produced greater plastic deformation, inducing higher surface hardness and compressive residual stress. Tensile tests demonstrated that the EP-LSP-treated samples exhibited an increase of 7.5% in yield strength, 8.4% in ultimate tensile strength, and 19.7% in elongation compared to LSP-treated samples. Further analysis of the microstructure revealed significant phase transformation and recrystallization in the EP-LSP-treated sample. The increasing dislocation density, nano-twins and grain refinement had contributions to the strength, with nano-twins having the most significant contribution.