Experimental in-situ verification of the unloading mechanics of dual phase steels

© 2019 Elsevier B.V. The paper presents the first experimental verification of dislocation repulsion during springback of Dual Phase (DP) steel, a mechanism which is suggested to cause non-linear unloading due to micro-plastic strain generation. In-situ loading-unloading tests are conducted within a Scanning Electron Microscope (SEM). It is shown that strain partitioning between ferrite grains as well as within a single ferrite grain occurs. It was observed that dislocations pile up during loading and repel or bow out during unloading. Only dislocations that were mobile during the initial deformation were able to move during unloading.