Joining of aluminum alloy AA6061 to mild steel was achieved using a friction stir extrusion (FSE) method in which processed aluminum was extruded into a preformed steel dovetail groove. These joints were subject to various in-process cooling (IPC) methods via compressed air, water, granulated dry ice, and liquid nitrogen as well as varying weld pitches (WP) via the following rotational and translational (inches per minute, IPM) weld parameters: 1500RPM-3IPM, 1500RPM-2IPM, 1000RPM-3IPM, and 1000RPM-2IPM. Rockwell hardness testing and lap shear tensile testing were then used to evaluate the effectiveness of IPC by comparison to uncooled joints. These tests revealed an increase of 4.1% and 3.1% of hardness performance of the water cooled and dry ice cooled respectively compared to the uncooled weld. Additionally, the average tensile shear joint strength increased at a maximum of 4.5% for water cooled joints, 3.7% for air cooled welds, 3.5% for dry ice cooled welds, and 1.8% for liquid nitrogen cooled welds. The use of various IPC sources also revealed that the higher the WP, the stronger the extrusion joint. Thus, WP (revolution per inch, RPI) in order of descending performance are as follows: 750 RPI, 500 RPI, and 333 RPI. The novelty of this IPC and WP research comes from the investigation on the FSE joints compared to past research that has used butt and lap welds. The introduction of IPC and varying WP improved the strength and hardness of the FSE joints with the water cooling yielding the greatest measured improvement.