Thermal history analysis of friction stir processed and submerged friction stir processed aluminum

In this research, equations are developed to model the rate of heat input from different geometries of friction stir processing (FSP) tools. The model is then compared with actual heat input obtained from embedded thermocouples within the stirred region. The cooling curves obtained from the thermocouple data are then applied to the Derby–Ashby model for high angle grain boundary migration to predict the final grain size of a bulk sample produced by the friction stirring method. Submerged friction stir processing (SFSP) is introduced as a way of increasing the cooling rate of the bulk samples in an attempt to decrease the grain size. Microstructures obtained from both FSP and SFSP are characterized using transmission electron microscopy.