Hybrid approaches of assisted heating and cooling for friction stir welding of copper to aluminum joints

Abstract

Heating assisted-friction stir welding (FSW) was carried out at different preheating currents of 40, 80 and 120 amps by applying tungsten inert gas torch ahead of stirring tool while, compressed air and water were brought into the effect behind the stirring tool in case of cooling enhanced FSW. The welded specimens were subsequently assessed by macro-graphs, optical microscopy, tensile and hardness analysis, scanning electron microscopy and X-ray diffraction characterization. Minor improvement in tensile strength of weld was reported by heating assisted FSW at low preheating current of 40 amp. Tensile strength of weld was deteriorated as preheating current increased to 80 and 120 amps. Significantly improved tensile strength was reported for weld of cooling enhanced FSW by water. Normal FSW and hybrid FSW were contained intermetallic compounds such as CuAl2 and Cu9Al4. The amount of intermetallic compounds formed in stir zone was increased as preheating current increased. The formation of intermetallic compounds was drastically reduced as cooling effect increased from compressed air to water. Higher hardness of stir zone was reported for both hybrid FSW techniques relative to normal FSW.