Strain rate dependence of tensile properties and strengthening mechanism of Ti6Al4V alloy undergoing different coverage layers of laser shock peening

Abstract

Understanding the response of the Ti6Al4V alloy undergoing different coverage layers of laser shock peening (LSP) and the strain rate dependence of tensile properties is indispensable for its wide applications. Herein, the Ti6Al4V alloy specimens subjected to different coverage layers of LSP were employed in the uniaxial tensile testing with the strain rate of 0.001 s−1, 0.005 s−1, 0.01 s−1, and 0.02 s−1. The effects of the coverage layer on the tensile properties and its sensitivity to the strain rate were determined. The relationship between the microstructural morphologies, tensile behaviors, and strengthening mechanism were revealed. Moreover, the corresponding fracture behaviors of the tested specimens were summarized. It evidently shows that, the tensile properties and fracture behaviors of the Ti6Al4V alloy subjected to LSP treatment strongly depend on the strain rate. The ultimate tensile strength and the total elongation exhibit reverse trends with increasing strain rates and coverage layers, also, the typical ductile fracture pattern gradually evolves into the mixed ductility/cleavage fracture simultaneously. Upon the increasing plastic deformation process of LSP, the dislocation density, as well as the grain size are two intrinsic factors for controlling the strain hardening behavior and strain rate sensitivity, and the deformation twin provides another alternative factor.