This document summarizes a study on heat flow prediction in friction stir welded aluminum alloy 1100. Experiments were conducted to determine the effect of tool rotational speed, weld speed, and tool pin diameter on temperature at the weld nugget and heat affected zone. A mathematical model was developed using regression analysis to predict temperature and heat flow based on the process parameters. An artificial neural network model was also developed and its predictions were compared to the experimental and mathematical model results. Microstructural analysis was performed to examine the effect of parameters on weld microstructure.