Study of Coercivity Origin in Mechanically Alloyed Co-Zr System

[ $Co_100-XZr_X$ ] (x=10-40) alloys were prepared by using a mechanical alloying technique. Phase constitution of the crystallised material depended on the annealing temperature. The $Co₈₂Zr₁₈$ alloy crystallised at lower temperature around $550^\circC$ consisted of $Co₂₃Zr_6$, $Co_5Zr$ and fcc-Co phases, while the alloy crystallised at higher temperature around $800^\circC$ consisted of $Co₂₃Zr_6$ and fcc-Co phases. Phase constitution of the crystallised material also depended on the chemical composition of the alloy. The material with lower Zr content less than 10 at% Zr consisted of $Co₂₃Zr_6$ and fcc-Co, and the material with higher Zr-content over 30 at% consisted of $Co_2Zr$ phase. The material containing 15-20 at% Zr consisted of $Co₂₃Zr_6$, $Co_5Zr$ and fcc-Co. Only the material containing $Co_5Zr$ phase exhibited substantial coercivity, and it was confirmed that coercivity in the mechanically alloyed Co-Zr alloy was originated from the $Co_5Zr$ phase.