T. J. Prater, A. M. Strauss, J. Davidson, M. E. Howell, Vanderbilt University, Nashville, TN; G. E. Cook, Welding Automation Laboratory Vanderbilt University, Nashville, TN
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 primary 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. Experimental data for butt welds of these MMCs performed at rotational speeds from 1000 to 2500 rpm and travel speeds between 3 and 10 inches per minute will be presented. Torque and load measurements are recorded and analyzed for this range of process parameters. The results of tensile tests and macrosections of the obtained joints will also be discussed. Since tool wear is a limiting factor in the joining of MMCs, tool wear will be periodically monitored using an optical comparator. The tool geometry considered in this study is the Trivex tool, a non-cylindrical smooth probe design that is effective in reducing the forces that act on the tool during a weld cycle. Trivex tools designed for the butt welding of ¼” plates were fabricated from two materials: h13 tool steel and Molybdenum. The probes of several of the Molybdenum tools were coated with diamond using a chemical vapor deposition (CVD) process. The effect of the tool material on the quality of the finished Al 6061/SiC/17.5p joint will be quantified. One objective of this research is to produce friction stir welds using the diamond-coated Molybdenum tool to determine whether they are comparable in quality to those performed using conventional tool materials, but with an appreciable reduction in tool wear and/or axial force.
Summary: This research will establish a welding envelope for the friction stir welding of Al 6061/SiC/17.5p using Trivex tools composed of h13 tool steel, Molybdenum, and Molybdenum coated with diamond using the Chemical Vapor Deposition (CVD) method. Tool wear, torque, load measurements, and results of tensile tests will be analyzed.
