Role of Scroll Shoulder and Pin Designs on Axial Force, Material Flow and Mechanical Properties of Friction Stir Welded Al–Mg–Si Alloy

Understanding the flow of plasticized material during friction stir welding was critical for producing quality welds. The tool geometry such as shoulder and pin designs play a significant role in altering the material flow characteristics. In the present investigation, scroll shoulder design with varying pins were addressed in the aspects of tool axial force, material flow and mechanical properties. Marker insert method was used to study the flow of plasticized material with copper as inserts. The results show that the pin geometry variation has showed a significant change in the axial force plot in the welding phase. The taper cylindrical pin tool (T S ) facilitated a constant force, hexagonal pin (T S ) H and pentagonal pin (T S ) P tools facilitated a decreasing force behavior, and triangular pin designed tool (T S ) T facilitated an increasing behavior of force in the welding phase. The material flow experiments showed that the scroll shoulder with triangular pin shaped tool (T S ) T completely sheared the marker inserts in both parallel and perpendicular to weld conditions compared to other pin shapes. The sheared copper fragments were uniformly distributed on both advancing and retreating sides of the weld for (T S ) T tool. Superior mechanical properties were noticed for (T S ) T tool with a tensile strength of 184 MPa and Microhardness of 78 HV at stir zone. Graphic Abstract