1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous MetalsLanzhou University of Technology Lanzhou 730050 P. R. China
2. College of Materials Science and EngineeringLanzhou University of Technology Lanzhou 730050 P. R. China
3. Department of Materials Science and EngineeringNational Tsing Hua University Hsinchu 30013 Taiwan, ROC