1. State Key Laboratory of Complex Nonferrous Metal Resources Clear Utilization, 253 Xuefu Road, Kunming 650093, P. R. China
2. Yunnan Provincial Key Laboratory for Nonferrous Vacuum Metallurgy, 253 Xuefu Road, Kunming 650093, P. R. China
3. National Engineering Laboratory for Vacuum Metallurgy, 253 Xuefu Road, Kunming 650093, P. R. China
4. Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, 253 Xuefu Road, Kunming 650093, P. R. China