高应变率拉伸下纳米空洞的成核与早期生长
摘要
The nucleation and growth of voids under high tensile strain rate are investigated using molecular dynamics method. Our simulation results show that dislocations of (111)-[211],(111)-[211],(111)-[211],(111)-[211] slip system are first initiated in concentration regions of defects and vacancies. Voids nucleate in vacancy strings that are generated via the continuous jogging of the stacking fault of specific slip system. Vacancy strings are along [011] and [011] directions and vertical to the loading directions. These specific slip systems overlap results in largest cross-sectional area of vacancy strings. Since then, the nucleated voids grow up via dislocation emission, and their shapes gradually evolve into strip-like, cylindrical, ellipsoidal, and spherical. In single crystal copper with double void inclusions, more slip systems are simultaneously initiated under the stress distribution of the existing voids. In this case, the new generated voids nucleate at the specific positions where the stacking faults of the three slip systems intersect. Influenced by the moving directions of dislocation lines, their shapes are first flat-triangle-like, and then gradually evolve to spherical-like with slipping and climbing of dislocations. We also calculate the vacancy volume in the junctions when three stacking faults encounter according to distortional filed distribution, finding that among 108 different crossing configurations, only four configurations result in maximum vacancy volume that enable void to nucleate, void can not nucleate in other condition.