Friction stir welding (FSW) is a solid-state process based on friction welding. In this study, the numerical simulation of the flow pattern for 2024 aluminum rod FSW was carried out using DEFORM-3D finite-element software. The temperature field and effective strain simulated welding with two 2024 aluminum rods at a rotational speed of 1800 rpm and a feed rate of the FSW of 0.2 mm/s. The rotation of the aluminum rods was stopped when the temperature at the contact surface exceeded the crystallization temperature of the materials; normal force was applied at the contact surface of the aluminum rod. The three-dimensional (3-D) material flow model of FSW resulted in numerical simulations that indicated that FSW can reduce residual stress in the materials and enhance the tensile strength of the weld surface.