Process-structure-property relationships for nugget and heat affected zone regions of AA2524-T351 friction stir welds

The effects of weld tool rotational speed omega, welding speed v and z-axis force F-Z during friction stir welding of the aluminium alloy 2524-T351 on the resulting process response variables, nugget microstructure, nugget tensile properties and heat affected zone hardness variations were investigated. For the range of conditions examined, the results indicate that omega has the dominant effect on nugget properties and structure, that optimum nugget tensile properties can be obtained by increasing omega to obtain a peak temperature that is just below the incipient local melting temperature, and that excessive values of v result in low nugget ductility because of localised embrittlement near the weld crown. The study has also shown that the peak weld temperature is inversely related to the measured torque T-0. The T-0-omega relationship appears to be a useful guide for weld modification, as it is indicative of conditions leading to overheating in the nugget region.