Analysis of microstructure and its effect on yield strength of pure alpha-titanium consolidated by equal channel angular pressing

Abstract

The recycling value of chips of pure alpha-Ti was demonstrated with eco-friendly equal channel angular pressing (ECAP) to replace energy intensive melting and casting. Electron backscatter diffraction (EBSD) was used to reveal the microstructure formed after single- or multi-pass ECAP, characterized by a heterogeneous structure containing high- and low-angle grain boundaries (HAGBs, with misorientation 215°, and LAGBs, <15°). Grain formation was analyzed by considering the shear strain due to tooling features of ECAP die, and thermal effect because of elevated temperature. The strength was properly predicted by the Bailey-Hirsch relation, consistent with the analysis of the contributions from alpha-matrix, HAGBs, and LAGBs, respectively. The paper makes clearly the underlying physical metallurgy principles to achieve high yield strength in pure alpha-Ti.