Computational analysis of novel AlLiMgTiX light high entropy alloys

Abstract

Phase formation rules include some terms and parameters are defined to predict the formation and stability of solid solution phases in light high entropy alloys (LHEAs). Calculation of the terms considering respective criteria for LHEAs, introduced the AlLiMgTiX alloy group (X = Zr, Nb) containing the lightest Al14Li11Mg35Ti15Zr25 alloy with theoretical density (ρth) of 3.36 g/cm3. Varying the atomic percentages of each composing element between 5 andto 35 in the AlLiMgTiX alloy group lead to a total of 3749 alloys with ρth less than or equal to 5 g/cm3. In theory, some terms like δ and Δχ representing atomic radii and electronegativity differences are used to design novel LHEAs, and minimizing values of such terms facilitates the formation of solid solution phases in the structure of LHEAs. According to calculations, Al10Li5Mg35Ti15Zr35 and Al20Li8Mg5Ti35Nb32 were the alloys with minimum values of Δχ and δ respectively. Hence, some experimental works were done to verify the design method and check the validity of terms in phase formation rules. On that account, the difficulties of alloying due to the presence of Li and Mg were overcome by reducing the total weight percentage of such elements resulting in the successful fabrication of bcc single solid solution phase Al21Li8Mg5Ti34Nb32 -LHEA via melting and casting method with a density of 5.28 g/cm3.