含与不含晶界空穴双晶体晶体滑移与应力场分析

ANALYSIS OF CRYSTAL SLIP AND STRESS FIELD IN BICRYSTAL WITH AND WITHOUT A VOID IN THE CRAIN BOUNDARY

基于晶体滑移理论对双晶体进行研究,考虑平行和垂直于外加应力方向的两种晶界(gain boundary,GB)状况,同时在晶界上引进空穴的影响。采用各向异性有限元程序对双晶体的应力场和滑移系开动规律以及微空穴的生长规律进行计算分析,考虑晶体取向的影响。结果表明,晶界的存在显著改变双晶体应力场,在晶界附近产生应力集中,对此两晶粒的取向有较大的影响;在相同的加载参数下,滑移系的开动主要取决于两个晶粒的取向差别;微空穴的长大与晶界类型和晶粒的晶体取向有强烈的依赖关系,其中垂直晶界更有利于晶体的滑移和微空穴的生长,滑移系开动后微空穴增长速率明显加快。文中分析表明,只有从细观的角度出发,才能准确理解晶界和微空穴对双晶乃至多晶材料的变形损伤规律和失效机理。

Based on finite deformation crystallographic constitutive theory, the bicrystals with a void and without a void in the grain boundaries （GBs） are studied, which are perpendicular and parallel grain boundary relative to the tensile axis. The stress distributions near the grain boundaries, the resolved shear stress of the slip systems and growth of the void are analyzed by three-dimensional anisotropic crystallographic Finite element method, taking the different crystallographic orientations into consideration. The numerical results of bicrystal models show that there are a high stress gradient and stress concentration near the grain boundary. The features of stress concentrations are dependent on the crystallographic orientation of the two grains. At the same loading parameter, the activating law of the slip systems is relative to the difference of the two grain＇ s crystallographic orientation. The volume of the void depends on crystallographic orientation and the direction of loading on the bicrystal. The void grows more easily in the perpendicular grain boundary. Also, the growth rate rises after slip systems are activated. The calculation indicates that it is only by the detail study of the stress distribution that the bicrystal and pelycrystal deformation, damage and failure can be understood deeply.