Non-dimensional modeling of the effects of weld parameters on peak temperature and cooling rate in friction stir welding

Experimental data from friction stir welded Al 7075 and HSLA-65 were used to create dimensionless, empirical models relating critical weld parameters to the peak temperature rise and cooling rate of the weld heat-affected zone. Five different backing plate materials and a wide range of travel speeds and weld powers were used in the experimental design to ensure the models are relevant to a broad range of welding parameters. The resulting models have R-squared values of 0.997 and 0.995 for the dimensionless peak temperature rise and cooling rate correlations, respectively. Demonstrations of the models' practical applications are provided. Herein is shown how the models can identify welding parameter (i.e. travel speed or power) levels needed to produce a desired weld peak temperature rise or cooling rate. Also demonstrated is how the models can be used to explore the relative effects of travel speed and backing plate thermal diffusivity on weld peak temperature rise and cooling rate.