Influence of Fe on Al4C3as a heterogeneous nucleation substrate: a first-principles study

To elucidate the influence of Fe on the crystal structure of Al4C3 and its carbonaceous refining effect on primary Mg grains, the adsorption energy and electronic structure of adsorption were investigated via first-principles calculations. The results show that H 1 and are the most stable adsorption sites for the Al-terminated and C-terminated Fe/Al4C3(0 0 0 1) adsorption systems. Based on their formation energies, the adsorption system is more stable than the H 1 adsorption system, indicating that Fe atoms should adsorb on the C-terminated surface rather than on the Al-terminated surface. Analyzing the atomic structure of the adsorption system revealed that the surface structure of Al4C3(0 0 0 1) is reconstructed when the adsorption coverage exceeds 0.25 ML of Fe atoms. Thus, Fe adsorption may weaken the heterogeneous nucleation potency of Al4C3 particles. This explains the observed experimental phenomenon that excessively high Fe contents negatively influence the refinement of Mg alloys with added carbon.