1. State Key Laboratory of Solidification ProcessingCenter for Nano Energy MaterialsSchool of Materials Science and EngineeringNorthwestern Polytechnical University Xi'an 710072 P. R. China
2. State Key Laboratory of Solidification ProcessingShaanxi Key Laboratory of Friction Welding TechnologiesSchool of Materials Science and EngineeringNorthwestern Polytechnical University Xi'an 710072 P. R. China
3. SEED Research CenterXi'an Economic & Technological Development Zone Xi'an 710014 P. R. China
4. Research Center of Nanoscience and NanotechnologyShanghai University Shanghai 200444 P. R. China