Investigation of coherency loss by prismatic punching with a nonlinear elastic model

Coherency loss of misfitting precipitates by nucleation of dislocations at the interface is investigated using a nonlinear elastic model. This is made possible because the model inherently takes into account, in addition to long-range elastic interactions, phenomena involving dislocation cores such as dislocation nucleation and cross-slip. It is also shown that the model naturally delivers viscous motion laws above a threshold stress. The mechanism of prismatic punching proposed by Ashby and Johnson is confirmed by the present work for small precipitates. For larger precipitates, more complex situations are predicted which involve several dislocations, beyond the scope of the available analyses, but often observed experimentally.