Microstructures and Magnetic Properties of Nd-Fe-B-X (X=Co, Zr) Alloys Produced by a Metallic Mold Casting Method

Abstract

The microstructures and magnetic properties of Nd₄Fe_77.5B_18.5 and Nd₄(Fe-X)_77.5B_18.5 (X=Co, Zr) alloys produced by a metallic mold casting were investigated. The resulting Nd₄Fe_77.5B_18.5 alloys had a cylindrical shape with 1 mm in diameter and 50 mm in length and had fine equiaxed grains. The cylindrical sample contained some metastable Fe₃B and amorphous phases together with the stable Fe₂B, Nd₂Fe₁₄B, and α-Fe phases. However, the coercivity of the cylindrical sample was as low as that of the original ingot. The substitution of Co or Zr for Fe in Nd₄Fe_77.5B_18.5 alloy resulted in a drastic change in the microstructures. These cylindrical samples showed a slightly higher coercivity than the Nd₄Fe_77.5B_18.5 counterparts.