The Onset of Slip Activity in Relation to the Degree of Micro-Texture in Ti-6Al-4V

Abstract

The mechanical properties of titanium alloys result from their complex multi-scale microstructural features such as micron scale precipitates and millimeter scale microtextured regions (MTRs). Deformation processes that operate at the scale of the α grain are of critical importance to mechanical properties, especially to fatigue performance. However, previous investigations also highlighted that the mm-scale MTRs affect the mechanical properties of titanium alloys. Specifically, MTRs promote long-range strain localization due to the low intergranular misorientation within a MTR. Furthermore, the elastic anisotropy of the alpha phase and the non-random spatial distribution of crystallographic orientations within the MTRs produce complex mechanical effects. The present work is a mechanistic investigation of MTRs using crystal plasticity simulations of mm3-scale experimentally captured and synthetically generated 3D microstructure datasets. The explicit modeling of both the α grains and MTRs in a titanium alloy is used to determine the effect of the degree of microtexture on the deformation behavior and on the onset of plastic slip. The presence of MTRs with a dominant [0001] orientation results in both stress and plastic strain hotspots during the early stages of straining. The influence of MTRs on the local stress and strain fields are analyzed and discussed with regard to the monotonic tension, fatigue and dwell-fatigue behavior of titanium alloys.