Tunable twin stability and an accurate magnesium interatomic potential for dislocation-twin interactions

Abstract

We showed that there are two variants of twin boundaries for each twin system in hexagonal close-packed materials in our previous study. In this work we further demonstrate that the mechanical stability of these two twin variants in Mg are controlled by their energies and theoretically tunable. In the second part of this work, we continue to incorporate this information of twin boundaries into a newly developed embedded-atom-method (EAM) potential for pure Mg. In addition to twins, the other important information of dislocations and stacking faults is also included, which renders our potential among one of the rare comprehensively optimized ones. Therefore our potential is supposed to be able to accurately capture the physics of not only single defect but also defect-defect interactions. The defect-defect interactions have not been adequately addressed, since modeling their long-range force fields based on density functional theory is computationally too expensive. The new potential will supply new momentum to the study of defect-defect (such as twin-dislocation) interactions and the defect-controlled mechanical properties in Mg. Our study therefore sheds light on the design of novel Mg alloys with optimized mechanical properties.