Simulations of a phase-field model based on Karma’s thin-interface asymptotics are carried out in a quantitative study of diffusion-limited crystal growth during isothermal solidification of aluminum-copper (Al-Cu) alloys. We observe a morphological transition from dendritic to seaweed growth as the undercooling exceeds a critical threshold, dependent on the alloy concentration. Such a transition is expected theoretically, with the theoretical morphology diagram thus far established only in two dimensions and for growth with thermal diffusion. The quantitative observation of this transition in three-dimensional simulations of a specific material represents a novel prediction. Details of the mechanism of the transition are examined and associated with prior theoretical perceptions, in particular about the order of the nonequilibrium phase transition. Experimental verification of our findings would not only test the robustness of the well-established general phase-field model but also confirm the extrapolation of simulation results from lower alloy concentrations to the higher concentrations typically used in experimental studies. Such validation would provide critical insights into the interplay between alloy composition, undercooling, and morphological evolution during solidification.
Schulz et al. (Fri,) studied this question.