Abstract
Nd12.6-xDyxFebal.CoyB6.2Zr0.1Ga0.3(x =0.3-1.9, y =5.8-18.3) alloys were processed by improved HDDR process with intermediate argon treatment and desorption under constant H2 pressure to increase remanence and coercivity, respectively. In this study, we investigated effect of Co and Dy contents on the magnetic properties of the HDDR powders. By the improved process, remanence of HDDR powders containing 0.3 at.% Dy and 12 to 16 at.% Co is increased to a maximum of 0.96 T, and coercivity of them containing 0.9 to 1.6 at.% Dy and 5.8 at.% Co is increased to the maximum of 1570 kA/m. Undecomposed (Nd, Dy)2(Fe, Co)14B phase remains in HDDR powders including Dy above the critical content expressed by the line drawn from 0.6 at.% Dy and 18.3 at.% Co to 1.9 at.% Dy and 7.8 at.% Co. The magnetic properties of the bonded magnets with density of 6.2 Mg/m3 made from the Nd12.0Dy0.6Febal.Co5.8B6.2Zr0.1Ga0.3 anisotropic HDDR powder areas follows: Br =0.87 T, HCJ=1530 kA/m and (BH)max =137 kJ/m3. Its temperature coefficient of remanence is -0.11%/°C and of coercivity is -0.43 %/°C.
