An Investigation into the Friction Stir Welding of Al 6061 and Al 6061/SiC/17.5p using Diamond Coatings

Abstract

Friction Stir Welding (FSW) is a solid-state joining process developed by The Welding Institute (TWI) in 1991. The large axial forces associated with this process are typically cited as one of the major obstacles to its widespread application. The primary objective of this research is to quantify the reduction of axial force through use of diamond coatings of FSW tools. Results of welds for coated and uncoated tools on Al 6061 are compared. The goal is to produce friction stir welds using the diamond-coated tool that are comparable in quality to those performed using conventional tool materials, but with an appreciable reduction in tool wear and/or axial force. A finite element solver is used to model the stresses and deformations for the coated and uncoated tools. Aluminum Metal Matrix Composites (Al-MMCs) are used in many naval and aerospace structures. An MMC material is comprised of two parts: a continuous metal matrix (in this case Aluminum) and reinforcing particles dispersed throughout the matrix. The secondary objective of this research is to parameterize the friction stir welding of Aluminum 6061 Metal Matrix Composites reinforced with 17.5 percent Silicon Carbide particles, a superabrasive material valued for its high strength to weight ratio. A range of acceptable process parameters for the joining of this material is established. Since tool wear is a limiting factor in the joining of MMCs, tool wear is periodically monitored and quantified using an optical comparator.