In polycrystalline magnesium(Mg)and Mg alloys,as the grain size decreases,the grain boundary(GB)mediated plasticity including GB sliding and GB migration becomes the dominant deformation mechanism.In this study,the motion of[1(1)00]symmetric tilt GBs in Mg bicrystals is investigated using molecular dynamics(MD)simulations.The effects of GB mis-orientation angle and temperature are considered.At low/room temperatures and varied GB misorientation angles in the range of θ ≥ 58.36°,the GB migration occurs via the shear coupling with the invariant plane of {0001};At 35.80°＜θ＜58.36°,both the GB migration and GB sliding happen and the invariant plane changes from {0001} plane to {11(2)2} plane;At 26.54° ≤ θ ≤35.80°,the GB migrates with the invariant plane of {11(2)2};Finally,at θ＜26.54°,the GB sliding becomes the main deformation mechanism.At 700 K,the GB sliding occurs at the misorientation angles in the range of θ＜58.36°;while the GB migration occurs at the misorientation angles of θ ≥ 58.36°.By comparing the energy barriers of GB migration and GB sliding,it yields that the deformation mode with a low energy barrier always happens,which leads to the transition of deformation modes and agrees well with the MD simulation results.
万方数据