Using ab initio calculations in designing bcc Mg-Li alloys for ultra-lightweight applications

摘要

Ab initio calculations are becoming increasingly useful to engineers interested in designing new alloys, because these calculations are able to accurately predict basic material properties only knowing the atomic composition of the material. In this paper, single crystal elastic constants of 11 bcc Mg-Li alloys are calculated using density functional theory (DFT) and compared with available experimental data. Based on DFT determined properties, engineering parameters such as the ratio of bulk modulus over shear modulus (B/G) and the ratio of Young's modulus over mass density (Y/rho) are calculated. Analysis of B/G and Y/rho shows that bcc Mg-Li alloys with 30-50 at. percent Li offer the most potential as lightweight structural material. Compared with fcc Al-Li alloys, bcc Mg-Li alloys have a lower B/G ratio, but a comparable Y/rho ratio. An Ashby map containing Y/rho vs B/G shows that it is not possible to increase both Y/rho and B/G by changing only the composition of a binary alloy.