A Simulation of Friction-Stir Processing for Temperature and Material Flow

Abstract

Utilizing a tool without a pin, cast AlSi9Mg aluminum alloy was modified by friction-stir processing. Since the tool design specifically targets the microstructure within the surface layers, the process is more appropriately termed friction-stir surfacing. A coupled numerical model of this special friction-stir process was developed to visualize the material flow patterns and temperature distribution. As the tool transports surface material from the leading edge toward the retreating side of the tool, the material follows the scroll of the tool shoulder toward the tool center with each tool rotation. At or near the tool center, the material flows into the workpiece thickness, forming the vortex of a process zone. Depending on the processing conditions, i.e., tool velocity and rotation speed, an upward material flow also develops within the process zone. Due to the flow of cooler, unprocessed material into the process zone, the temperature profile on the tool/workpiece interface is skewed toward the advancing side and leading edge with higher processing temperatures occurring in these locations. However, the process parameters influence the shape and magnitude of the temperature distribution on this surface.