Microstructure and coercivity variation in melt-spun Sm-Co-Fe-Zr ribbons

Sm13.94Co69.67Fe12.34Zr4.06 alloy was melt-spun at wheel speeds (WS) of 15, 30 and 60 m/s in order to obtain ribbons with two phase microstructure. Structural and magnetic properties of as-spun and annealed ribbons were investigated using X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. Microstructural studies revealed that the ribbons melt-spun at 15 m/s were composed of the Sm2Co7 phase along with the SmCo5 matrix phase, while the ribbons prepared at higher wheel speeds (30 and 60 m/s) showed co-existence of the soft magnetic phase Fe with the hard magnetic SmCo5 phase. The grain size of the ribbon was found to decrease with the increase of the WS. Demagnetization curves as well as the XRD studies showed presence of two phases. Unconventional grain refinement was observed in melt-spun ribbons at 60 m/s after annealing at 600 °C for 10 min. Annealed ribbons (60 m/s) exhibited exchange coupled demagnetization behavior with a coercivity of 17.2 kOe.