Sm 12Co 59Cu 6Fe 20Zr 3 sintered magnets made from as-cast alloy and melt-spun ribbons

Abstract

A comparative study between Sm 12Co 59Cu 6Fe 20Zr 3 master alloy magnet and melt-spun ribbon magnet is made by applying the same traditional sintering-solid solution-aging-slow cooling method. The X-ray diffractometer, electron microscope and magnetometer are employed to investigate the structure and magnetic properties of the magnets. It is found that two types of sintered magnets are formed both of which have Th 2Zn 17-type main phase. Master alloy sintered magnet has a typical cellular structure, with average cell size of 88.3 nm and cell wall width less than 20 nm, and the comprehensive magnetic properties are: H ci = 21.1 kOe, M r = 75.9 emu/g and M s9T = 107.8 emu/g. The coercivity of the ribbons melt-spun at a speed of 20 m/s is merely 2.1 kOe, while in ribbon sintered magnet, this value can approach as high as 27.4 kOe, together with remanence 61.8 emu/g and maximum magnetization M s9T = 103.6 emu/g. A typical cellular–lamellar microstructure is obtained in ribbon sintered magnet, with average cell size of 102.3 nm, cell wall width less than 10 nm and lamellar size of 1–3 nm. The high-coercivity of ribbon sintered magnet can be attributed to the following factors: the existence of lamellar phases, larger cell size, thinner cell walls, more cell boundary phases and desirable composition distribution.