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

Super-transus heat treatments conducted on an additively manufactured body-centred-cubic beta-Ti alloy led to the formation of equiaxed beta 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. IMPACT STATEMENT Columnar to equiaxed transformation of beta by super-tranus heat treatment of SLM-fabricated Ti is due to Rayleigh instability and grain growth, dismissing the belief that usual deformation-driven recrystallisation is responsible.