A dislocation-based model for cyclic plastic response of lath martensitic steels

Softening behavior of lath martensitic steels is related to the coarsening of laths and dislocation evolution during cyclic deformation. Involving the physical mechanism, we developed a dislocation-based model to study the cyclic plastic response for lath martensitic steels. For a block, we proposed an interfacial dislocation evolution model to physically present the interaction between mobile dislocations in the block and interfacial dislocations by considering the coarsening mechanism of the laths. Moreover, the evolution behavior of backstress caused by dislocation pile up at the block boundary has been considered. Then, a hierarchical model based on the elastic-viscoplastic self-consistent (EVPSC) theory is developed, which can realize the scale transition among representative volume element (RVE), prior austenite grains (PAGs) and blocks. According to the proposed model, the effective mechanical responses including the cyclic hysteretic loop and peak stress at different cycles for lath martensitic steel have been theoretically predicted and investigated.