1. aSchool of Material Science and Engineering, Central South University, Changsha, Hunan, P. R. China
2. bKey Laboratory of Non-ferrous Metallic Materials Science and Engineering, Ministry of Education, Changsha, Hunan, P. R. China
3. cHunan Sushi Guangbo Testing Techniques Co. LTD, Changsha, Hunan, P. R. China