Concurrent model for sharp and progressive columnar to equiaxed transitions validated by directional solidification experiments processed in microgravity conditions

Columnar and equiaxed structures, which occur during solidification of metallic alloys, influence the texture properties castings, welded joints additively manufactured components. During transient solidification, where grain refiner particles provide predominant nucleation mechanism, a to Equiaxed Transition (CET) occurs when conditions that had originally favoured directional columnar growth change those favouring equiaxed. Constitutional undercooling ahead front can permit growth. By carrying out experiments in microgravity conditions, liquid flows due thermal solutal buoyancy effects are suppressed. In these diffusion-controlled we have observed examples both sharp (clear) progressive (gradual) CET. The experimental outcomes, especially observation CET, has highlighted need for continuum model allows competitive structure development; hence, Concurrent (C2ET) is proposed. C2ET thermally relies on well-known concept extended impingement mechanics; thereby, greatly reducing numerical complexity. Importantly, proposed approach removes specific equiaxed-blocking criterion, often as an essential requirement other CET models. validated by four scenarios: two velocity jumps thermal-gradient decreases. induced CETs; whereas, decreases gave CETs. good agreement transition zones Results compared with classic Hunt model. Unlike Hunt’s model, predicted all macrostructure transitions faithfully using single (or consistent) set input parameters across scenarios. Since, same level refinement was used each experiment, consistent expected. enable effective simulation at lower computational cost industrial processes rely processing step.