Deformation-free geometric recrystallisation in a metastable beta-Ti alloy produced by selective laser melting

Abstract

Super-transus heat treatments conducted on an additively manufactured body-centred-cubic β-Ti alloy led to the formation of equiaxed β grains from an initially columnar structure. The grain structure was transformed thanks to a combination of Plateau-Rayleigh instability and grain growth driven by reduction in grain boundary surface area. This is a new type of geometric recrystallisation with no deformation involved. Other mechanisms proposed based on either deformation-induced recrystallisation or martensitic decomposition are dismissed owing to low dislocation density and absence of martensitic transformation in the alloy studied. Columnar to equiaxed transformation of β by super-tranus h..