镁单晶沿不同取向压缩的变形机制分子动力学研究

Study on molecular dynamics of compression deformation mechanism of different orientations of magnesium single crystal

基于分子动力学理论,建立沿C轴以及<1010 >(垂直C轴)方向进行单轴压缩的模型,结合两种模型的应力-应变曲线,分析镁单晶沿不同取向压缩的微观变形机制。结果表明,沿C轴压缩时模型的压缩弹性模量较大,说明该取向难变形。且该模型先发生基面不全位错滑移(柏氏矢量b1^→=1/3<1010 >)以及锥面位错滑移(柏氏矢量b2=1/6<0223 >),其次在位错畸变区形核产生{1011}孪晶。此外,在晶体内部观察到两种不同类型的{1011}孪晶变体。沿垂直C轴方向压缩过程中,首先会形成大量的紊乱点,为位错以及孪晶的产生提供形核点。进一步加载时,会出现{1012}孪生过程,且{1012}孪晶迅速吞噬基体,模型变为沿C轴方向压缩变形,最后在位错堆积的畸变区形核生成{1011}二次孪晶。

Molecular dynamics theory was used to build two models of uniaxial compression in the direction of the C-axis and <10]-0 > (vertical to the C-axis).The micro deformation mechanism of magnesium single crystal compressed along different orientations was analyzed combining the stress-strain curves of two models.The results show that the compressive elastic modulus of the compression model along the C-axis is larger,which means that it is more difficult to deform in this orientation.Partial dislocation (the Burgers vector bl is 1/ 3<1010 >)of basal and dislocation (the Burgers vector b2 is 1/6<0223 >)of pyramidal plane are observed firstly.Then the {1011} twin emerges at the dislocation distortion zone.In addition,two different types of {1011} twin variants are observed inside the crystal.In compression process along the vertical C-axis,a large number of disordered points are formed to provide nucleation points for dislocation and twins.After further loading,{1012} twin is generated,and the twin devours the matrix rapidly.The modal becomes compress deformation along the C-axis.At last {1011} secondary twin is generated from the distortion area where the dislocation accumulates. Key words:magnesium single crystal;orientation;plastic deformation mechanism;twin;molecular dynamics