摘要
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[1100]symmetric tilt GBs in Mg bicrystals is investigated using molecular dynamics(MD)simulations.The effects of GB misorientation angle and temperature are considered.At low/room temperatures and varied GB misorientation angles in the range ofθ≥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[1122]plane;At 26.54°≤θ≤35.80°,the GB migrates with the invariant plane of[1122];Finally,atθ<26.54°,the GB sliding becomes the main deformation mechanism.At 700 K,the GB sliding occurs at the misorientation angles in the range ofθ<58.36θ;while the GB migration occurs at the misorientation angles ofθ≥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.
在多晶镁及其合金中,随着晶粒尺寸的减小,晶界塑性(晶界滑移、晶界迁移等)变为主要的变形机制.本文采用分子动力学模拟方法研究了晶界倾斜角度和温度对双晶镁中[1100]对称倾斜晶界的运动的影响.在低温和室温下,当晶界倾斜角度θ≥58.36°时,发生以{0001}面为不变面的剪切耦合晶界迁移;当35.80°<θ<58.36°时,晶界迁移和晶界滑移同时发生,晶界迁移的不变面逐渐由{0001}面变为{1122}面;当26.54°≤θ≤35.80°时,发生以{1122}面为不变面的晶界迁移;最终,当θ<26.54°时,晶界滑移成为主要的变形机制.在温度为700 K时,晶界滑移在θ<58.36°时发生;而晶界迁移在θ≥58.36°时发生.通过比较晶界迁移和晶界滑移的能垒,可以发现能垒更低的变形机制优先发生,从而导致变形机制的转变,这与分子动力学模拟的结果相符.
基金
supported by the National Natural Science Foundation of China(Grant Nos.12192210,12192214,and 12072211)。
