Development of Yttria-dispersed CoFeNi medium entropy alloy: morphological evolution and magnetic properties

Abstract In the present work, equiatomic CoFeNi and (CoFeNi) 99 (Y 2 O 3 ) 1 medium entropy alloys (MEAs) were prepared by mechanical alloying. The addition of Y 2 O 3 in the CoFeNi MEA phase evolution, morphological and magnetic characteristics were examined by x-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. Based on DSC studies, the annealing temperature for CoFeNi alloy powder was 400 °C determined. The Phase analysis revealed that both as milled, with and without Y 2 O 3 alloys showed single-phase FCC. No phase change was observed after annealing. Both milled and annealed powders showed an irregular shape morphology and maintained the equiatomic composition of elements. Adding Y 2 O 3 to CoFeNi MEA showed high magnetic saturation (98.94 emu g −1 ) and coercivity (95.47 Oe). Post-annealing, the alloy powder exhibited further enhanced magnetic saturation (114.57 emu g −1 ) and decreased coercivity (76.27) Oe. The successful dispersion of a small amount (1at%) of Y 2 O 3 in the CoFeNi alloy, followed by annealing, was responsible for the improved magnetic characteristics, corresponding to an increase in the pinning effect.