Iranian Journal of Materials Science and Engineering

Friction stir welding (FSW) is a promising technique to join aluminum alloys without having problems encountered during fusion welding processes. In the present work, the evolution of microstructure and texture in friction stir welded thin AA2024 aluminum alloy are examined by electron backscattered diffraction (EBSD) technique. The sheets with 0.8 mm thickness were successfully welded by friction stir welding at the tool rotational speeds of 500, 750, and 1000 rpm with a constant traverse speed of 160 mm/min. EBSD revealed that stir zones exhibited equiaxed recrystallized grains and the grain size increased with increasing the tool rotation rate. The fraction of high angle grain boundaries and mean misorientation angle of the boundaries in the FSW joints at 500 rpm were 63.6% and 24.96°, respectively, which were higher than those of the sample welded at 1000 rpm (53.6% and 17.37°). Crystallographic texture results indicated that the Cube {001}<100> and S {123}<634> textures in base metal gradually transformed in to Copper {112}<111> shear texture. It was found that with increasing the tool rotation rate, the intensity of Cube {001}<100>, Y {111}<112>, S {123}<634>, and Dillamore {4 4 11}<11 11 8> texture orientations increased and the intensity of Brass {011}<211> texture orientation decreased. 

One of the interesting state-of-the-art approaches to welding is the process of friction stir welding (FSW). In comparison with the fusion processes, FSW is an advantageous method as it is suitable for the non-fusion weldable alloys and polymeric materials joining. Regarding the materials pure solid state joining, it also provides joints with less distortion and enhanced mechanical properties. In the present work, a three-dimensional (3D) model based on finite element analysis was applied to study the thermal history and thermomechanical procedure in friction stir welding of high density polyethylene plate. The technique includes the tool mechanical reaction and the weld material thermomechanical procedure. The considered heat source in the model, includes the friction among three items: the material, the probe and the shoulder. Finally, the model was validated by measuring actual temperatures near the weld nugget using thermocouples, and good agreement was obtained for studied materials and conditions.