1. GM Global R&D Center, Warren, MI 48090-9055
2. The Ohio State University, Columbus, OH 43210
3. Department of Industrial and Manufacturing Engineering, 310 Leonhard Building, The Pennsylvania State University, University Park, PA 16802
4. Center for Friction Stir Processing, Department of Materials Science and Engineering, Advanced Materials and Manufacturing Processes Institute, University of North Texas, Denton, TX 76203
5. Center for Friction Stir Processing, Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203