1. State Key Laboratory of Solidification ProcessingCenter of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical University Xi'an Shaanxi 710072 P. R. China
2. School of Physics and ElectronicsHunan University Changsha 410082 P. R. China
3. Key Laboratory of Materials Processing and Mold (Zhengzhou University)Ministry of EducationZhengzhou University Zhengzhou 450002 P. R. China
4. School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore