The role of thermomechanical processing routes on the grain boundary network of martensite in Ti–6Al–4V

The influence of thermomechanical processing (TMP) of a Ti–6Al–4V alloy on the transformation texture and intervariant boundary network were investigated by conventional EBSD mapping along with the five-parameter boundary analysis approach. The texture characteristics of Ti–6Al–4V subjected to deformation in the β regime followed by the β→α martensitic transformation were examined using visco-plastic self-consistent simulation and forward calculation of the transformation texture. Comparison of the simulated and experimental texture characterisitcs revealed that the transformed α′ texture was dominated by the variant selection associated with substructure development in the β parent phase and the occurrence of specific self-accommodating α′ variants in the microstructure, promoting the quadrilateral and/or V shape variant arrangement. This resulted in a progressive increase in the 63.26°/[10‾553‾] intervariant boundaries with the strain increment, at the expense of 60°/[112‾0]. Moreover, the grain boundary network for all conditions was dominated by the triple junctions (grain boundary network) terminating on 63.26°/[10‾553‾] and 60°/[112‾0] intervariants. It is shown that the elastic interactions among the variants during the martensitic transformation is the dominant parameter affecting the grain boundary network, despite the presence of dislocation based variant selection.