Peak temperature arising during the joining of metals by friction stir welding (FSW) needs to be investigated along with other process parameters of FSW to understand their inevitable impact on joint quality. This investigational and experimental analysis aims to determine the impact of pin geometry and its rotational speed by formulating thermic mechanical process-based models to anticipate peak temperature and to compare it with actual values. Three distinctive pin geometries rotated at three speeds were used while other parameters were unchanged. The fitness and suitability of the model were verified by comparing the anticipated values with the experimental values. Macrographic and micrographic observations revealed that flawless joints with improved mechanical properties were fabricated at a peak temperature of 616 K (80 % melting temperature) when a taper cylindrical pin with a rotational speed of 818 rpm was employed. In addition, SEM analysis of the fractured specimen confirmed that failure of the defect free weldment occurred in brittle mode, indicating that preferred fusion of grains and their constituents occurred during the joining process. Compared with other solid-state and unconventional welding techniques, such as electron beam welding, laser beam welding, and plasma arc welding, FSW is cheaper and more cost effective and does not require filler material and shielding medium (or gas), strict safety measures due to the absence of molten spatter and toxic fumes, skilled labor, long operation period, and cool down period, thereby boosting production rate and efficiency; moreover, FSW can be employed to fabricate joints in all positions, including horizontal, vertical, and overhead [12][13][14].