Investigation of Dynamic Recrystallization on the Root Side of FSW Joints

The grain size is basically influences the mechanical properties of welded joints. During friction stir welding (FSW) different grain sizes occur on the welded joint as a function of wall thickness and joint zones [1] [2]. The main goal is to reach the fine grained structure in whole joint. According to the literature [3] [4] [5] the dynamic recrystallization (DRX) can occur during friction stir welding and it can cause extra fine grains. This can be determining for the aspects of tool design and technological parameter optimization. The weakest part of a friction stir welded joint is the root because the circumstances are not always good for dynamic recrystallization, so coarser grains are appeared there. Therefore the investigation of dynamic recrystallization on the root side is important for technological parameter optimization.