A Grand-Potential Based Phase-Field Approach for Simulating Growth of Intermetallic Phases in Multicomponent Alloy Systems

Abstract

Intermetallic phase-based alloys, in particular transition-metal aluminides, are potential structural and coating materials for high-temperature applications. Such applications usually involve interdiffusion between two dissimilar materials. To simulate interdiffusion microstructures quantitatively, it becomes essential to solve alloy phase-field models in conjunction with multicomponent CALPHAD databases. This coupling, however, still remains a challenge when considering binary or multicomponent intermetallic phases. Here, a novel method that incorporates successfully diffusion potential dependent-properties of bulk multicomponent phases into a grand-potential based multi-phase-field model is proposed. It uses phase-specific properties directly precomputed from CALPHAD-type databases as discrete functions of solute diffusion potentials. Six different alloy cases, ranging from a five-phase binary (Ni-Al) to a two-phase quaternary (Al-Cr-Ni-Fe) alloy, are simulated to illustrate the application and correctness of the method. The cases include both substitutional and intermetallic phases. Where a comparison is possible, the simulations show good agreement with DICTRA and experimental results, thus validating our proposed method. In contrast to our approach, we find that DICTRA fails in three of the simulations involving ordered intermetallics. We further show that the interface width in this model can be varied without accuracy loss, thus enabling computationally affordable simulations at experimentally comparable length and time scales.