剪切力作用下螺位错的运动

THE MOVEMENT OF SCREW DISLOCATIONS UNDER SHEAR STRESS

利用分子动力学方法研究了金属钨中螺位错在剪切力作用下的运动特性.根据弹性理论在BCC晶体中形成位错线沿<111>的螺位错,在合适的边界条件下获得平衡态的位错结构.发现位错由{110}平面沿<112>方向三个呈对称的皱褶组成.对平衡态结构施加剪切力,发现剪力很小时,位错核心不动,核心形状有畸变;当剪力增大到一定程度时位错开始运动.位错运动后,剪切力较小时,核心呈“之”字形运动;在较大剪力下,位错开始阶段呈“之”字形运动,一段距离后主要沿[211]方向作直线运动.位错运动的速度随着剪切力的增加而增大.

The movement character of screw dislocation in tungsten under shear stress is studied by using molecular dynamics method. The screw dislocation is formed according to the elastic theory. Equilibrated atomic structure containing screw core is obtained with proper boundary conditions by relaxation. It is found that the equilibrium dislocation has three-fold symmetry and spread out in three 〈 112 〉 direction on （ 110） planes. Shear stress is acted on the atomic structure. When the stress is small, although the shape of the dislocation core changes, the screw dislocation doesnt move. After the stress is larger than a certain value, the dislocation begins to move. At the beginning of the dislocation moves, the dislocation moves in zigzag. When the shear stress gets larger, the dislocation will move almost in [ 211 ] direction in a straight line. We have also found that the velocity of dislocation core becomes higher as the shear stress increases.