Influence of mechanical milling on structure, particle size, morphology and magnetic properties of rare earth free permanent magnetic Zr2Co11 alloy

Abstract

In an effort to explore finding rare earth free permanent magnet material for device applications, the Co based Zr2Co11 compound has been selected for investigation. A detailed study was carried out on the effect of mechanical milling on structure, particle size, morphology and magnetic properties. The alloy of nominal composition Zr18Co82 exhibited co-existence of minor Zr6Co23 phase along with main phase Zr2Co11. When subjected to long duration mechanical milling, the alloy has undergone structural disorder leading to partial amorphization. The particle size has decreased from 200 μm to 120 μm up on milling for 6 h in a planetary milling process. Further milling caused less influence on particle size reduction. However, it had an effect on particle size distribution. The size reduction is not very high due to ductile nature of Zr2Co11 phase and the morphology of the particles too showed coarse plate shape. The coercivity variation against particle size reduction is less than appreciable, given that the crystal structure being rhombohedral with significant magnetocrystalline anisotropy. The defects induced during milling and the presence of deleterious minor phases are considered the main cause for reduction in the coercivity.