SHOCK-INDUCED DISLOCATION NUCLEATION AND EVOLUTION IN Mg-3Al-1Zn ALLOY WITH INITIAL VOID

Due to the demand for lightweight materials in automotive and aerospace fields, magnesium and its alloys play an irreplaceable role due to a series of advantages such as low density and high strength. Currently, Mg-3Al-1Zn alloy is one of the most widely used commercial magnesium alloy. It is of great significance to study its deformation mechanism and shock response of Mg-3Al-1Zn alloy. In this paper, molecular dynamics method has been used to study the shock behaviors of Mg-3Al-1Zn alloy with a cylindrical void. For 0001 and \text10\bar \text1 \text0 oriented Mg-3Al-1Zn specimen, the nucleation and evolution of dislocations near void surface induced by shock wave are discussed. Simulation results show that the activation of slip system near the void is strongly dependent on the shock orientation. In 0001 orientation, basal dislocations preferentially nucleate near the void, and basal lattices near void are found to be rotated by ~ 21° and finally form a high-angle grain boundary. However, prismatic dislocations are observed to be the preferentially mode along the \text10\bar \text1 \text0 orientation, subsequently, a large number of basal dislocations nucleated. Based on the theory of stress wave, it is found that the dislocation behaviors near the void are greatly affected by the reflected isometric wave (SV ₂), while the plastic deformation behaviors associated with void collapse are greatly affected by the irrotational wave (P ₂). Moreover, the distributions of the shear stress near the void are analyzed to predict the distributions of the nucleated dislocation under different shock orientations. In general, simulation results in this paper are in good agreement with the prediction based on stress wave theory and the distributions of the resolved shear stress, and the nucleation and evolution mechanisms of the dislocations near the void are obtained.