William A. Curtin¹, Rasool Ahmada¹, Binglun Yin¹, Zhaoxuan Wu²; ¹Institute of Mechanical Engineering, École Polytechnique Fédérale de Lausanne, ²Institute of High Performance Computing

Pure Mg has low ductility due to a transition of pyramidal dislocations to a sessile basal-oriented structure [1]. Dilute alloying generally improves ductility. Enhancement of pyramidal cross-slip from the lower-energy Pyr. II plane to the higher energy Pyr. I plane has been proposed as the mechanism [2]. Here, the theory is applied to ternary and quarternary alloys of Zn, Al, Li, Ca, Mn, Sn, K, Zr, and Sr at dilute concentrations, and a wide range of compositions are predicted to have good ductility [3]. Interestingly, while Zn alone is insufficient for achieving ductility, its inclusion in multicomponent alloys at 0.5at% enables ductility at the lowest concentrations of other alloying elements. Further implications of the theory are discussed.[1] Z. Wu, W.A. Curtin, Nature 526 (2015) 62-67[2] Z. Wu et al., Science 359 (2018) 447-452[4] R. Ahmad et al., Acta Materialia 172 (2019) 161-184