Variant selection and intervariant crystallographic planes distribution in martensite in a Ti–6Al–4V alloy

Abstract

The transformation texture was studied in a Ti–6Al–4V alloy for two microstructures produced through different phase transformation mechanisms (i.e. diffusional vs. displacive). Both microstructures revealed qualitatively similar crystallographic texture characteristics, having two main texture components with Euler angles of (90°,90°,0°) and (90°,30°,0°). However, the overall α texture strength was considerably weaker in the martensitic structure (i.e. displacive mechanism) compared with the α+β microstructure produced through slow cooling (i.e. diffusional mechanism). The intervariant boundary distribution in martensite mostly revealed five misorientations associated with the Burgers orientation relationship. The five-parameter boundary analysis also showed a very strong interface plane orientation texture, with interfaces terminated mostly on the prismatic planes {hki0}, when misorientation was ignored. The highest intervariant boundary populations belonged to the 63.26°/[10‾553‾] and 60°/[112‾0] misorientations, with length fractions of 0.38 and 0.3, respectively. The former was terminated on (41‾3‾0), and the latter was a symmetric tilt boundary, terminated on (1‾011). The intervariant plane distribution in martensite was determined more by the constraints of the phase transformation than by the relative interface energies.