Effect of knurling shoulder design with polygonal pins on material flow and mechanical properties during friction stir welding of Al–Mg–Si alloy

Abstract

Abstract Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications. The optimal tool shoulder and pin design combination, which plays a vital role in material flow was addressed. The flow of plasticized material was analyzed using a marker insert technique. The results show that the knurling shoulder design with square and hexagonal pin design facilitated constant stability force with reference to weld length/time. The uniform mixing and distribution of plasticized material were facilitated by the knurling shoulder design with square tool pin shape (TK)S (sticking length minimum) below which fragmented copper was observed. (TK)S tool facilitated higher mechanical properties for the welds, i.e. strength (182 MPa) and hardness (HV 78) in stir zone.