Strongly out-of-equilibrium growth morphologies in fast solidifying eutectics

Abstract

In metal printing processes such as laser-based additive manufacturing, typical solidification velocities yield a strongly out-of-equilibrium (SOE) growth regime that is intermediate between the slow solidification in conventional metal casting and rapid solidification regimes characterized by severe solute trapping. Using phase-field simulations supported by experimental observations, we provide evidence for an inherent growth mode of the SOE regime in slightly hypereutectic Al-Ni, leading to the destabilization of the planar eutectic coupled growth front and the development of a protruded state. We interpret this scenario theoretically in terms of a concomitant growth of different solidification modes, here the coupled eutectic together with $\ensuremath{\alpha}$ primary phase. As another example of concomitant growth under SOE conditions, we present simulation results for single-phase solidification of a Ni fcc-phase exhibiting dendrites and doublons.