Role of grain size and crystallographic texture on tensile behavior induced by sliding mechanism in Ti-6Al-4V alloy

The aim of this paper is to investigate the coupled effects of grain size and crystallographic texture on the mechanical behavior induced by gliding mechanism in Ti-6Al-4V alloy. Thus, four microstructures of Ti-6Al-4V alloy whose grain size and crystallographic texture are different were examined by tensile tests along the rolling direction at room temperature. In this study, the contribution of gliding on basal < a >, prismatic < a > and pyramidal < c + a > plans in the accommodation of plastic strain was estimated by means of a slip trace analysis. The role of the individual grain size and the crystallographic texture was then statistically evaluated. Based on the results of slip trace analysis, numerical optimizations of the Critical Resolved Shear Stress < CRSS > of basal < a >, prismatic < a > and pyramidal < c + a > in the four microstructures were then carried out, using transition scale rules and a local behavior model. The results suggest that the mechanical behavior of Ti-6Al-4V is controlled by the activation of slip systems that depend not only on their CRSS but also the initial orientation and size of each individual grain. The low CRSS of prismatic < a > slip systems can lead to early activation of these systems in favorably oriented coarse grains. Therefore, a local plastic deformation can be shown. At high levels of loading, increasing the grain size can minimize the crystallographic texture effects by deforming the unfavorably oriented coarse grains. Moreover, based on the results of the numerical optimization, it can be also suggested that the CRSS can decrease with the increase in grain size according to the local Hall Petch relationship.