Effect of pre-twinning on deformation mechanism of [0001]-textured nanocrystalline Mg by molecular dynamics simulation

The effects of pre-twinning on the mechanical behavior and deformation mechanism of [0001]-textured nanocrystalline magnesium (NC Mg) were investigated using molecular dynamics simulations. By introducing different types of twins, it is found that pre-twinning results in a softening effect on the strength of textured NC Mg, and this effect is more pronounced with the misorientation angle of the twin boundaries decreases. The introduction of twin boundaries reduces the accumulation of dislocations and the concentration of stress at the grain boundaries, thereby improving the ductility of textured NC Mg. In addition, pre-twinning promotes the formation of twin chains during loading, thereby reducing interface misorientation and further promoting intergranular dislocation slip. With the migration of twin boundaries, the pre-twinned NC Mg exhibits a coordinated deformation mechanism of small grains assisting large grains. Furthermore, when the loading direction is at an acute angle to the c-axis of the pre-twin, the migration rate of the twin boundary is enhanced, resulting in detwinning or complete twinning of the grains. The current work provides new insights and ideas for improving the mechanical properties of textured NC Mg by pre-twinning.