基于点缺陷扩散理论与离散位错动力学耦合的位错攀移模型研究

Dislocation climb model based on coupling the diffusion theory of point defects with discrete dislocation dynamics

位错的攀移运动对高温下晶体材料的塑性行为有重要影响,为了能够有效揭示攀移的物理本质及其对塑性行为的作用,本文基于点缺陷扩散理论,通过将体扩散和管扩散机理的共同作用与三维离散位错动力学耦合,建立了适用条件更广的位错攀移模型.利用此模型我们模拟了单个及多个棱柱型位错环的收缩变形过程,发现影响位错攀移速率的决定因素不是传统理论认为的机械攀移力,而是位错周围(体扩散)及位错段上(管扩散)的空位浓度梯度.该模型也能够完全重现棱柱型位错环群的粗化过程中不同位错环半径及晶体内平均空位浓度随时间变化的三个阶段.

Dislocation climb plays a vital role in the plastic behavior of crystals at high temperatures. In order to reveal the intrinsic mechanism of climb and its effect on plasticity, a new dislocation climb model is first developed based on the combination of the diffusion theory with both bulk diffusion and pipe diffusion in a three-dimensional discrete dislocation dynamics （DDD） simulation, which is considered to be more physical and widely applicable. Using our model the shrinkage processes of a single prismatic loop group and prismatic loop group are simulated. It is concluded that the climb rate is not directly determined by mechanical climb force as believed in classical theories, but by the gradient of the vacancy concentration around （bulk diffusion） and along （pipe diffusion） the dislocation line. Loop coarsening process is also simulated, and the three pronounced evolving stages of the loop radii and the average vacancy concentrations in crystal are reproduced.