Investigation of silicon sublattice substitution within (Al,Si)3Zr intermetallics via DFT simulations

Aluminum alloys commonly contain Si as an impurity or alloying element. The energetic behavior of Si within multiple compounds and solutions is incorporated inside thermochemical packages, such as FactSage. This tool allows determining the Si partitioning within complex multiphasic systems. Recent experimental research suggests that Si can be found within Al3Zr-based intermetallics. Nevertheless, current FactSage databases do not consider the potential substitution of Si within the Al3Zr-D023 solid solution. In this work, Si substitution within the (Al,Si)3Zr-D023 phase was investigated by means of first-principles calculations. Replacement of Al atoms by Si resulted in a negative enthalpy of mixing, indicating that Si substitution is energetically enabled. The density of states (DOS) for both a Si-diluted (Al,Si)3Zr and a non-Si-doped (Al3Zr) simulation cells were analyzed. It is shown that (even in dilution), Si significantly impacts the electronic structure of the Al3Zr-D023 structure. Specifically, the presence of Si localizes electrons in the p orbital of Al, and increases the DOS of the dxy, dxz, and dyz sub-orbitals of Zr at low energies. Thus, yielding a coupled effect that stabilizes the D023 intermetallic. These findings are a benchmark for the future integration of a Si-based end-member within the Al3Zr-D023 solid solution of FactSage databases.