Analysis of the changes in microstructure, mechanical, and contact properties of multi-pass friction stir processed dp800 steel

Abstract

In this study, the friction stir process (FSP), which can be successfully applied to plate-type materials, was applied to DP800 steel in a varying number of passes (1, 2, and 3 passes), and the effects of the FSP on the microstructure, hardness, and strength values of the steel were examined. In addition, the changes in the strength values after the FSP were transferred to the finite element (FEM) and artificial neural network (ANN) based contact problem models, and the changes in the contact stress and areas were determined comparatively. As a result of the examinations, it was determined that there were significant reductions in grain sizes in the microstructure compared to the pre-processed material at all pass numbers after FSP. As a result, the hardness and strength values of the steel increased after FSP. FEM and ANN analyses revealed that maximum contact stress values increased after FSP due to higher strength, while contact area values decreased proportionally.