STUDY ON FRICTION STIR SPOT JOINT ON Al 6061 SHEET

Abstract

lriction Stir Spot Welding (FSSW) was performed on 6061-14 Aluminum alloy to investigate the effect of varies tool geometries and processing parameters on lap shear strength. In this welding process, four tool geometries were used viz: tapered pin flat shoulder tool (lSSW-]'l). cylindrical pin hat shoulder tool (FSSW-Cl ), cylindrical pin concave shoulder tool (FSSW-C2) and triangular pin concave shoulder tool. FSSW joint were investigated in respect of macrostructure, microstructure. microhardncss, lap shear strength and scanning electron microscope (SEM). SHook' was formed in FSSW joint region between the overlapped metal sheets. I-look length was significantly influence by the tool pin geometry. Weld made with FSSW-l2 has more hook width than FSSWC2 under the same process parameters. Grain size was found to increase on approaching from stirred zone (SZ) to base metal (BM). Microhardness of stirred zone was more than other zone. In SZ, inicrohardness by using FSSW-T2 was greater than microhardness by using FSSW-C2. Lap shear strength was more at high tool rotational - speed and low plunge rate. Tool rotational speed of 1 800 rpm and plunge rate of 0.03 mm/rev were optimum processing parameter (1 800 rpm & 0.03 mm/rev). Under optimum processing par, imeter. maximum lap shear separation load of about 2.14 KN & 1.85 KN were observed by using lSSW-12 and FSSW-C2 tool. lormation of intermetalhic layer at the joint interface and the fracture locations were studied using scanning electron microscopy (SEM).