Relationship between Microstructure, Residual Stress and Thermal Aspect in Friction Stir Welding of Aluminum AA1050

Abstract

Abstract Residual stresses (RS) are present in many fabricated structures due to local plastic deformation from thermal and mechanical operations during manufacturing such as Friction Stir Welding. The among the objectives of FSW is used to obtain high quality of joining which means eliminate defects, minimize heat input and/or high mechanical properties. The case of FSW process is more complicate since it leads to the development of residual stress in welded zone and, also, in TMAZ, caused by tool rotation. In the present paper, the effects of the thermal actions on the residual stress field occurring in FSW of AA1050 were investigated. Residual stress are measured in center of welded zone and in different distances from the joint for both retreating and advancing sides by XRD. Experimental results showed that residual stress in welded zone in FSW are higher when stirring rate increased. Also, the central zone of the joint is affected by large deformations resulting from a chaotic movement behind the tool. In this region, the grains of the base metal are fragmented by the tool and undergo dynamic recrystallization.