Fe self-diffusion in Fe-Al-Si melts – A combined ab initio molecular dynamics and experimental study

Abstract

The Al-Fe-Si system and its binary subsystems Al-Fe, Fe-Si and Al-Si are commonly used versatile alloys. Understanding the structural, dynamic and thermophysical properties of binary and ternary Al-Fe-Si alloys in the liquid and supercooled state before solidification is crucial to ensure the desired microstructure and therefore ideal product properties. With an increasing iron content in the alloy, the liquidus temperature increases and exceeds 1000°C for most ternary Al-Si-Fe alloys. At these high temperatures, experiments are more delicate to perform, making it challenging to obtain information on transport coefficients and (partial) structure factors. We present a combined first principle-based molecular dynamics (AIMD) simulations and experimental study of Al-Fe melts. Measurements were performed using quasi elastic neutron scatting (QENS) to obtain the self-diffusion coefficients of Fe at different Al-Fe compositions as a function of temperature. Simulations show that the slowing down of the dynamics observed in the experiments with respect to pure Al [1] might be due to the significant increase of the icosahedral ordering. By using such a combined approach, we intend to achieve in the future an improved simulation scheme using machine learning that realistically covers a larger range of the phase diagram, which cannot be easily assessed with experiments.