Influence of Solidification Rate on Microstructures of Cast Strips and Corresponding Sintered NdFeB Magnets

The influences of solidification rate on the microstructures of cast strips and corresponding sintered NdFeB magnets were investigated. The experimental results show that the volume fraction and size of columnar grains vary with the wheel speed V, and the fraction is highest to more than 90% with 3.5 μm in average width at V = 2 m·s−1. The reasons for the improved magnetic performance were discussed based on the micromagnetic theory and microstructure analyses of the strips and sintered magnets. The magnetic properties of sintered NdFeB magnets made from the (Nd, Dy)13.0(Fe, Ga, Al)80.5B6.5 cast strip which was obtained at V = 2 m·s−1 are as follows: B= 1.15 T(11.25 kG), iHc = 2799 kA·m−1 (35.2 kOe) and (BH)max = 242 kj·m−3(30.35 MGOe).