NdFeB material composed of what?
Author：Cixi Nengli Magnetics Co., Ltd. Add Time：2014/7/22 13:49:53
The main raw material NdFeB rare earth metal neodymium, iron and non-metallic elements and boron (sometimes with the addition of aluminum, cobalt, praseodymium, dysprosium, terbium, gallium, etc.), generally expressed as:
RE2TM14B (RE = Nd, Pr, Dy TM = Fe, Co)
NdFeB permanent magnet materials based on Nd2Fe14B ternary compounds as substrates, its composition should be similar to the compounds Nd2Fe14B formula. But exactly Nd2Fe14B composition ratio, the magnets can be very low, or even non-magnetic. But the actual content of neodymium and boron magnets were neodymium and boron content than Nd2Fe14B compound for a long time (that is, the formation of the Nd-rich phase and boron-rich phase) in order to obtain better magnetic properties.
· Phase matrix Nd2Fe14
This phase is the main phase of the magnet, and its volume (after the ingot has been substantially fixed Lianwan) determines the magnetic remanence (Br), maximum magnetic energy product ((BH) m), the magnetic field orientation is achieved when forming it distribution such that the molecular arrangement of the easy axis of the structure (C) are ordered along the orientation direction, in order to achieve higher magnetic properties.
· B-rich phase
B-rich phase in the matrix in the presence of a compound, which is a non-magnetic phase, the magnetic properties are generally harmful, but rather the presence of a B-rich phase is easily broken so that the ingot.
· Nd-rich phase
Most of Nd-rich phase exists in Nd-Fe compound is present, it has to increase the density of the magnet during the sintering process has a very important role. Because of its nature very lively, so it is easily oxidized to form an oxide phase, the corrosion resistance of the magnet is very unfavorable. However, Nd-rich phase is relatively long, long crystal ingot for good, you can reduce the precipitation of α-Fe.
Observation showed that large amounts of tissue, the microstructure of sintered NdFeB-based alloy having the following characteristics (a) a matrix phase (main phase) of a polygonal grains; (2) B-rich phase exists in isolation or granular bulk; (3) the Nd-rich grain boundary phase along the grain boundaries or cross-coupling of the distribution; (4) In the base there are other impurities such oxide phase and voids.