Microstructure Changes for HDDR-processed Nd-Fe-B Powders with Different Al and Nd Contents

摘要

Microstructures of hydorogenation-decomposition-desorption-recombination (HDDR) processed Nd-Fe-Co-B-Ga-Zr-Al magnetic powders with different Al and Nd contents were investigated by a high-resolution scanning electron microscope (HRSEM) and an analytical transmission electron microscope (ATEM), in order to understand the relationship between the microstructures and the coercivities. By the addition of 1.5 at%Al, it was found that the area fraction of the Nd-rich GB phase decreases from 3.6 to 1.8 %. However, very thin GB phase is formed uniformly around each Nd_2(Fe,Co)_(14)B grain and then the coercivity increases from 15.3 to 17.0 kOe. By increasing up to 13.5 at%Nd, the fraction of Nd-rich GB phase increases drastically to 7.1 %, resulting in the further increment of coercivity (18.1 kOe). These results suggest that the formation of Nd-rich GB phase is very effective in the improvement of coercivity.