Effect of tool plunge depth (TPD) on the microstructure and mechanical properties of FSW dissimilar joints reinforced with SiC nano particles

Abstract

The effect of varying tool plunge depth (TPD) on the distribution of silicon carbide (SiC) nano particle reinforcement in fabricating the composite friction stir weld (FSW) dissimilar joints of aluminium alloy plates of 2024-T351 to 7075-T65 was investigated. Taper threaded cylindrical (TTC) tool is employed to produce the composites at the weld nugget zone (WNZ) of FSW dissimilar joints by varying the TPD range 5.80 mm to 6.20 mm, and keeping the tool rotation speed (TRS), 1000 rpm, tool traverse speed (TTS), 40 mm/min and tool tilt angle, 2°, as constants. The microstructure studies carried out using optical microscopy (OM) and scanning electron microscopy (SEM) indicates that the interaction of tool probe, tool shoulder with materials and SiC reinforcement plays a significant role on weld joint properties. The lower TPD results in insufficient heat generation causing SiC nano particle to stretch towards the retreating side (RS). Higher TPD leads to adhering of particle to tool shoulder and decreased flow of material to advancing side (AS) of the weld region. The optimum TPD of 6.10 mm results in uniform distribution of SiC in the WNZ with a higher micro-hardness of 150 Hv and ultimate tensile strength (UTS) of 389 MPa, yield strength (YS) of 213 MPa and percentage elongation (%EL) of 10.7.