In this paper, we present the effects of subtituting elements of M (Ti, Si and Nb) and annealing temperatures on the structure and magnetic properties of Co79-xZr18+x-yMyB3 alloy ribbons (x = 0 - 2, y = 0 - 4). Hard magnetic properties of the alloy ribbons can be strengthened so significantly as a coercivity of Hc > 4 kOe and maximum energy product of (BH)max > MGOe with an appropriate concentration of Ti, Si or Nb and annealing process. | Investigation of fabrication of Co-Zr based rare earth-free hard magnetic alloys by Melt-Spinning method Vietnam Journal of Science and Technology 56 (1A) (2018) 14-24 INVESTIGATION OF FABRICATION OF Co-Zr BASED RARE EARTH-FREE HARD MAGNETIC ALLOYS BY MELT-SPINNING METHOD Nguyen Van Duong1, 2, *, Nguyen Mau Lam1, Duong Dinh Thang1, Nguyen Huy Ngoc3, Pham Thi Thanh2, 4, Nguyen Hai Yen2, 4, Do Bang4, Luu Tien Hung5, Nguyen Huy Dan2, 4 1 Hanoi Pedagogical University No 2, No 32 Nguyen Van Linh, Phuc Yen, Vinh Phuc, Viet Nam 2 Graduate University of Science and Technology, VAST, No 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam 3 VNU University of Engineering and Technology, No 144 Xuan Thuy, Cau Giay, Ha Noi, Viet Nam 4 Institute of Materials Science, VAST, No 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam 5 Nghean College of Education, No 389, Le Viet Thuat, Vinh, Nghe An, Viet Nam * Email: duongnvsp2@ Received: 15 August 2017; Accepted for publication: 5 February 2018 ABSTRACT Co-Zr based alloy has attracted much interest of potential to replace the rare earth- containing hard magnetic materials due to its high coercivity. In this study, we investigated the effects of subtituting elements of M (Ti, Si and Nb) and annealing temperature on the structure and magnetic properties of Co79-xZr18+x-yMyB3 alloy ribbons (x = 0 - 2, y = 0 - 4). The alloy ribbons with a thickness of 20 µm were prepared by melt-spinning method with a rolling speed of 40 ms-1. A part of the melt-spun ribbons was annealed at different temperatures from 550 to 800 oC for various durations from 2 to 15 minutes. Their structure and magnetic properties were investigated by X-ray diffraction (XRD) and a pulsed field magnetometer (PFM), respectively. The results of the XRD analysis showed that two soft magnetic phases, namely Co and Co23Zr6, coexist with a Co5Zr hard magnetic phase in the alloy ribbons. The fraction of these .
