The invention discloses a method for preparing a high-
coercivity neodymium-iron-
boron magnet through
grain boundary diffusion, and belongs to the field of magnetic materials. Low-melting-point
metal is one of Ga, Zn and Sn, low-melting-point
alloy is prepared from R-M, R is one or more of La, Ce, Pr, Nd, Gd, Tb, Dy, Ho and Y, and M is one or more of Cu, Al, Ga, Sn and Ag. The method comprises the process steps that the surface of a
neodymium-iron-
boron magnet is cleaned firstly, then the
magnet is subjected to vacuum preheating, and the magnet is placed in a vacuum melting
metal or
alloy solution for hot
dip coating to achieve
surface coating; finally, the
neodymium-iron-
boron magnet obtained after hot
dip coating is subjected to diffusing heat treatment and subsequent annealing treatment, the
boundary structure and
grain boundary phase distribution of the magnet are improved, and the needed high-
coercivity neodymium-iron-boron magnet is obtained. The magnet
surface coating is even and high in binding strength, and uniformity of the
grain boundary diffusion process and the structure and performance of the magnet are promoted; meanwhile, the thickness of an attached layer on the surface of the magnet can be flexibly controlled by controlling
dip coating time and taking-out speed, and waste of
diffusion source
metal or
alloy is avoided; the heat dip
coating process is continuous, fast and suitable for volume
continuous production.