Atomistic insight into three-dimensional twin embryo growth in Mg alloys

Abstract

AbstractMagnesium (Mg) alloys are essential for industrial applications but poorly understood from a mechanistic perspective, while a comprehensive understanding of their mechanical behavior can guarantee a more efficient alloy design as well as a greater application potential. As one of the key deformation mechanisms in Mg and Mg alloys, twinning is investigated in this work. Molecular dynamics simulations are used to perform a systematic study of the effect of alloying elements and solute compositions on twin embryo growth in nine Mg alloys. The alloying elements include Al, Zn, Li, Ca, Pb, Nd, Ce, Sn, and Y, covering a wide range of element properties such as lattice constant, bulk/shear modulus, and cohesive energy. We demonstrate a faster migration of the dark side than the bright side of twin embryos in both pure Mg and Mg alloys. All solute atoms tested in this work exhibit a pinning effect on the motion of twin facets on the dark side. The motion of facets on the bright side, particularly twin boundaries, can be accelerated by solutes. Therefore, the majority of solutes can reduce the velocity difference between the dark side and the bright side of the twin. The overall twin embryo growth is restricted in most alloys except Mg–Y, Mg–Li and Mg–Nd with certain solute concentrations. Our results present important insight for tailoring twin structures and hence the mechanical properties of Mg alloys. Graphical abstract