Fully coupled thermo-mechanical finite element modeling of friction stir processing of super duplex stainless steel

In the present paper, a 3D thermo-mechanical finite element model (FEM) was developed to simulate friction stir processing (FSP) of super duplex stainless steel (SDSS SAF 2507). It aims to study the developed bead residual stresses and thermal history of the processed material. The model was built and solved in the Abaqus environment by considering the temperature dependency of the mechanical and physical properties of the investigated material. The Gaussian moving heat source was adopted to simulate the heat generated by the tool-workpiece interaction and was applied with the help of a developed user subroutine. Similarly, the tool forging force was incorporated as a moving surface load. For validation purposes, FSP was experimentally performed at a fixed rotational speed of 400 rpm, traverse speed of 100 mm/min, and tilt angle of 2°. During the process, the tool-workpiece temperature was measured using an infrared camera. After processing, the developed residual stresses within the processed zone were measured using the drill hole technique. The numerical results were found to agree with measured temperatures and residual stresses. FEM was then used to estimate the temperature history, the residual stress distribution, and the deformation contours in the processed SDSS SAF 2507. The numerically estimated results revealed a broadening in the plasticized zone within the plunging area. Moreover, developed stresses were found to stabilize within 40 mm from the starting point, i.e., two shoulder advancements. According to the estimated temperature history, the sigma phase was predicted not to form.