Effect of Thermal Assistance on the Joint Quality of Al6063-T5A During Flow Drill Screwdriving

An increase in fuel economy standards has affected automakers' decision toward designing lightweight vehicles and therefore transitioning from steel-based bodies to ones predominantly composed of aluminum. An introduction to lightweight materials couples that of lightweight joining with a thermomechanical process, flow drill screwdriving (FDS). This process is favored in terms of robustness, short installation time, and only requiring access to one side. The current limitation with FDS occurs with the imposed 8.3 N·m maximum installation torque standardized for M5 self-tapping screws. Warm forming of aluminum has been shown to increase ductility and formability of the material, and thus a reduction in installation torque is sought after along with an expected decrease in process time. In this study, different preprocess material temperatures of Al6063-T5A are studied to determine the effect of material temperature on the process time, installation torque, and other joint measurables. As a result, with the thermal assistance, a reduction in the process time up to 52% and installation torque by 20% was attained. The increase in preprocess material temperature did not affect the hardness of the material outside of the minimal heat-affected zone, as the maximum preprocess material temperature did not exceed the tempering temperature.