Thermomechanical and Material Flow Analysis during Friction Stir Welding of Marine Grade Aluminum Alloy 5083

This research aims to depict the thermal history, residual stress distribution, axial force applied, and material flow behavior on aluminum alloy 5083 (AA5083) plates, during the friction stir welding (FSW) process. This alloy finds most its use in shipbuilding industries and for marine constructions. It has been developed using an explicit, fully coupled thermomechanical nonlinear finite element (FE) analysis approach. The analysis was performed to simulate the effect of three stages, namely plunging, dwelling, and welding, of the FSW process. The ABAQUS/Explicit program was used for the computational modeling. To build a reliable and computationally efficient FE model, features such as arbitrary Lagrangian-Eulerian (ALE) formulation, adaptive meshing/ remeshing approach, mesh sensitivity analysis, and mass scaling have been introduced. The interaction between the tool bottom surface and the plate top surface was defined using a finite sliding and a sticking property. A Coulomb friction model with a temperature-dependent coefficient of friction (COF) was used to describe the tool-workpiece interaction. In addition, a small experiment was done with the following process parameters; a rotating tool speed of 875 rpm, a traverse speed of 60 mm/min, and a tool tilt angle of 0° to produce a defect-free butt joint to validate the numerically generated thermal profiles. The temperature was found slightly higher on the advancing side (AS). Residual stress distribution created over the whole width of the plates was also investigated. The introduction of friction stir welding (FSW) process by The Welding Institute in 1991 (Thomas 1991) drew much attention. During fusion welding of 5 mm AA5083 plates, the heat input should be very high. Because of this high input, a higher thermal gradient is produced, which leads to the formation of several intermetallic compounds (IMCs). Because of this IMC formation, the strength of the welded joint is reduced. However, the steep thermal gradient produced leads to the formation of finer microstructure near the weld bead and coarser along the base metal region. These results in the heterogeneity of the weld bead microstructure leading to less efficiency and accuracy of the weldment.