Effect of amorphous phase on the plastic deformation mechanism of Mg: A molecular dynamics study

Improving the plasticity of Mg alloys is an important frontier topic in the field of mechanics and materials. The influence of introduction of amorphous phase, grain size and temperature on the deformation mechanisms of nano-polycrystal Mg under tensile loading here is studied by molecular dynamics simulation method. The results indicate that the introduction of amorphous grain can improve the plasticity of the nano-polycrystal Mg due to cooperative movement of atoms in crystalline and amorphous phases. With the decrease of grain size, the plastic deformation of crystal phase in crystal-amorphous Mg-MgAl nanocomposites change from the nucleation of dislocations and growth of tensile twins to the grain boundaries glide and grains rotation, and the plastic deformation mode of amorphous phase change from the shear band dominated deformation to the homogeneous plastic deformation. The results also show that the amorphous grain plays a more and more important role during plastic deformation of Mg-MgAl nanocomposites as grain size decreases, and the deformation behavior of nanocomposites obviously depends on temperature. In addition, some quantified analysis about the deformation mechanism of nanocomposites is also presented.