Computational Modeling of Friction Stir Processing for DP780 Steel

Friction stir processing is a complex multiphysics phenomenon involving severe plastic deformation, material flow, heat transfer, and microstructure evolution, making its modeling highly challenging. Experimental approaches to optimize processing parameters are often costly and time-intensive. This study develops a computationally efficient model using COMSOL Multiphysics v6.2 to simulate the friction stir processing of DP780 steel, integrating JMatPro to provide alloy design and material properties. Key phase transitions observed include austenite formation around 1200 °C and ferrite emergence between ~800 °C and ~ 600 °C, with carbides such as M23C6, M7C3, and cementite present. Critical transition temperatures are Ac1 at 750 °C and Ac3 at 900 °C, while the peak temperature (~1490 °C) remains localized in the processed zone. The results demonstrate finite element analysis as a powerful tool for optimizing processing parameters, offering insights into temperature distribution, thermal history, and material flow, thus minimizing experimental efforts and costs.