A new approach to nuclei identification and grain refinement in titanium alloys

Abstract

An outstanding challenge in the production of titanium components by Additive Manufacturing (AM) is to promote the Columnar to Equiaxed Transition (CET) of the primary β-phase. This paper investigates the potential for quasi-stable elemental particles (Mo, Nb, W) to act as potent heterogeneous nucleant substrates for the Ti β-phase during arc melting and wire arc additive manufacturing. It is found that Mo, Nb and W-based particles act as potent nucleants during solidification and can facilitate the formation of refined equiaxed grains. A new mechanism for the efficacy of these particles is proposed, which is based on particle dissolution and its effects on supercooling and crystal growth. A new way of predicting potent quasi-stable nucleant particles is also presented.