Abstract
Pr-0.75 Y Co-0.25(5)-based as-cast alloys were processed by high-energy ball milling to obtain nanostructured powders with high coercivity. The powders obtained after 4 h of milling exhibited nearly amorphous behavior in X-ray diffraction patterns. DSC scans of the as-milled powders indicated a process of crystallization by broad, exothermic transition peak at 503 A degrees C. Annealing of the milled powders at 850 A degrees C for 2.5 min in high vacuum produced fine grains of size ranging 15-30 nm with optimal microstructure and hard magnetic properties. Magnetic measurements of the annealed powders evaluated a high intrinsic coercivity, (i) H (c) of 9.3 kOe, and a remanence ratio, M (r)/ M (max) of 0.72. The magnetic hardening was attributed to higher anisotropy field of the powders and microstructural uniformity achieved by the processing methodologies.