Multiscale discrete dislocation dynamics simulation of gradient nano-grained material

Prof. Xu Zhang

School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu, PR China

21. January 2019, 17.00
WW8, Room 2.018, Dr.-Mack-Str. 77, Fürth

Gradient nanostructured materials have synergetic strength and ductility. Multiscale discrete dislocation dynamics (DDD) method can track the evolution of dislocation microstructures and thus can help reveal the underlying mechanisms for curtain plastic behavior. However, the DDD investigations on gradient nano-grained metals are few due to the lack of a reasonable grain boundary (GB) model. In the present study, we first introduce a penetrable GB model, which is suit for arbitrary GB types, to the DDD framework. Then we conduct the DDD simulation to investigate the uni-axial compression of gradient nano-grained (GNG) polycrystals. The simulated results show that the dislocations initially activate and multiplicate in the larger grains, then propagating to the smaller grains gradually. The flow stress and strain hardening rate of the gradient nano-grained samples are higher than the value calculated by the rule of mixtures. It turns out that the extract hardening of gradient nano-grained materials may come from the back stress induced by GNDs accumulation in front of GBs.