采用分子动力学模拟方法对纳米双晶镁裂纹扩展的微观机制进行研究和分析，用EAM势描述镁原子之间的相互作用。结果表明：在拉伸载荷下，随着旋转界面角的增大，晶界由离散点状变为线状且晶界能量变大；裂纹扩展从裂纹尖端开始，经历“锐化-钝化-锐化”的循环变化过程；在界面角较大时，由于晶界的存在使其对裂纹扩展起到阻碍作用，裂纹扩展速率减小。因此，从理论上讲可通过将晶粒旋转合适的角度来提高有裂纹缺陷的双晶镁材料的韧性。
Molecular dynamics simulation was applied to investigate the deformation mechanism of bicrystal magnesium with cracks. EAM potential was selected to describe the relationship between magnesium atoms. The result shows that with tilt angles increasing,the grain boundary(GB)turns from dot into threadiness under tension loading. The crack propagates from the tip of crack and experiences cyclic deformation process such as“sharpening-blunting-sharpening”. The propagation velocity of crack decreases with larger tilt angle and the crack is blocked by grain boundary. Therefore,it is viable to promote the toughness of bicrystal magnesium with crack by rotating the tilt angle in proper degree.
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