1. State Key Laboratory of Advanced Welding and Joining; Harbin Institute of Technology; Harbin 150001 P. R. China
2. School of Materials Science and Engineering; Harbin Institute of Technology; Harbin 150001 P. R. China
3. Department of Physics; Harbin Institute of Technology; Harbin 150001 P. R. China
4. Shenyang National Laboratory for Materials Science; Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110016 P. R. China
5. Micro/Nano Technology Research Center; Harbin Institute of Technology; Harbin 150080 P. R. China