Effect of Cu Addition on the Microstructure and Magnetic Properties of an Fe₃B/Nd₂Fe₁₄B Nanocomposite Magnet

Abstract

The microalloying effect of Cu addition on the microstructure and magnetic properties of Fe₃B/Nd₂Fe₁₄B nanocomposite permanent magnets has been investigated. With the optimum heat-treatment condition, Cu-containing alloy exhibits a much finer nanocomposite microstructure. Three-dimensional atom probe (3DAP) results have revealed that Cu and Nd form a high density (∼10²⁴m^-3) of Cu-Nd clusters containing 5.0 at.% Cu and 7.0 at.% Nd prior to the crystallization reaction of the Nd_4.5Fe_76.8B_18.5Cu_0.2 amorphous alloy. These clusters serve as heterogeneous nucleation sites for the Fe₃B primary crystals. In the final Fe₃B/Nd₂Fe₁₄B nanocomposite microstructure, Cu dissolves uniformly in the Nd₂Fe₁₄B hard magnetic phase. Improved magnetic properties have been obtained in the Cu-containing alloy; these are attributed to the reduction in the grain size due to the addition of Cu.