Effect of tool offsetting on friction stir welding of dissimilar aluminium matrix composite and aluminium alloy

Commercial 6061 Al alloy and SiCp reinforced 6092 Al matrix composite (AMC) were joined by friction-stir welding (FSW) with different tool offsets. Results show offsetting the pin to Al alloy side could significantly reduce tool wear, while maintaining ultimate tensile strength of the joint around 180 MPa. As tool offset increased from zero to 3 mm, pin and shoulder wear length reduced from 0.17 mm to almost zero and from 0.28 to 0.02 mm, respectively. The corresponding estimated maximum safe welding length increased from 568 to 3125 mm. Fe debris were generated from the steel pin by the sharp SiC particles, then transferred into the nugget zone, eventually formed Al8Fe2Si particles during the FSW process.