Alloy Design and Fabrication of Ingots of Al-Mg-Li-Ca Light-Weight Medium Entropy Alloys

Abstract

  Alloy designs of light-weight high and medium entropy alloys (LW-HEA and LW-MEA, respectively) are discussed in relation to solving the problem of the empirical alloy parameter, ΔH_mix, and the difficulties of the fabrication process. The ingots of newly-designed Al-Mg-Li-Ca LW-MEAs were fabricated by the conventional casting process via crucible melting without using a vacuum furnace, and cast under air atmosphere. The ΔH_mix parameter is the average value of the mixing enthalpy of ΔH_i-j between the two components, i-j, in multicomponent alloys, and the dispersion of ΔH_i-j cannot be evaluated. The parameter δ (ΔH_mix) was suggested for the evaluation of the dispersion of ΔH_i-j. The Al-Mg-Li-Ca LW-MEAs were designed based on empirical alloy parameters, including δ (ΔH_mix). The alloy ingots of equiatomic AlMgLiCa, non-equiatomic Al₂MgLiCa, and AlMgLiCa_0.3 were successfully obtained by the conventional casting process. The solidification microstructure of the ingots in the Al₂MgLiCa LW-MEA was investigated, with particular focus on the position dependences of the chemical composition, constituent phases, solidification microstructure, and hardness. The present study clarified that LW-HEAs and LW-MEAs containing Al, Mg, Li, and Ca can be obtained by the conventional casting process under air atmosphere, without specific expensive casting equipment.