1. School of Physics and Optoelectronic Engineering Shandong University of Technology Zibo 255049 P. R. China
2. School of Mechanical Engineering Shandong University of Technology Zibo 255000 P. R. China
3. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou 730000 P. R. China
4. College of Mechanical and Electrical Engineering Shaanxi University of Science & Technology Xi'an 710021 P. R. China
5. School of Physical Science and Technology Lanzhou University Lanzhou 730000 P. R. China
6. Department of Superalloys, Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 P. R. China