Dislocation mobility and the mechanical response of BCC single crystals: A mesoscopic approach

A mesoscopic simulation of dislocations and plasticity in b.c.c. crystals at low temperatures is developed and applied to the case of Ta. The thermally activated nucleation of double kinks is taken as controlling the mobility of screw dislocations. The resulting temperature and strain rate dependence of the yield stress are investigated and a detailed thermal activation analysis is performed on the output of the simulations. It is shown that within the simplifications made to the input parameters and slip geometry, one is able to simulate realistic dislocation structures and mechanical response. By checking the conformity between the input and output, it is shown that the essential dislocation property (activation energy for screw dislocation motion) can effectively be deduced from the mechanical rests. The mesoscopic simulation provides a potential tool to link atomistic studies at the microscopic scale to the macroscopic modeling of mechanical properties of b.c.c. metals at low temperatures.