This work describes a three-dimensional mathematical model that provides insights as to the mechanism of heat generation during friction stir fabrication. We have explored the effect of processing parameters on the microstructure of the processed samples. Optical microscopy shows that the stratification of layers within the weld and the depth of the weld are both dependent on the processing parameters. EBSD analysis coupled with Vickers microhardness measurements of the processed pieces show that the grain size within the weld nugget is constant over the range of processing parameters available to the system. Data also show that pressure and heat inherent in friction stir processing of strain-hardened Al5083 counteract strengthening of the temper of the alloy.

Dr. Gray graduated with a Ph.D. from Virginia Tech in 2010. His research interests include non-destructive inspection, magnetic materials, and ferroics.