Main raw materials of ndfeb permanent magnet with a rare earth metal neodymium iron and boron nonmetal elements, metal elements (
Sometimes adding aluminum, cobalt, praseodymium, dysprosium, terbium, gallium, etc. )
, the general expressions for the: RE2TM14B (
RE = Nd,公关,Dy TM =铁、Co)
Ndfeb permanent magnetic material based on Nd2Fe14B ternary compound as matrix, its content should be close to compound Nd2Fe14B formula is.
But according to Nd2Fe14B composition ratio in full, magnets, magnetic can is very low, even no magnetic.
Only actual of neodymium magnets and boron content than Nd2Fe14B compounds and neodymium boron content (
The form rich and rich boron phase neodymium)
To get better performance of permanent magnet.
Matrix Nd2Fe14 phase, this phase is the main phase of magnets, its volume percentage (
A reasonable fixed after smelting ingot)
Determines the residual magnetism of the magnet (
, the maximum magnetic energy product (
, and forming the distribution of magnetic field orientation is to implement it to the molecular structure of the magnetic axis (
Orderly arrangement along the direction of orientation, so as to realize higher magnetic performance.
, wealthy phase B and B phase in the substrates by a certain compounds exist, it is a non magnetic phase, the magnetic can generally be harmful, but there is a rich phase B makes the ingot easily broken.
Rich, rich Nd phase Nd most to a Nd - exist
Fe compound exists, it to improve the density of magnets in the sintering process has a very important role.
Because of its nature is very lively, so it's easy to form oxide phase oxidation, corrosion resistance of magnets is very adverse.
But relatively rich Nd phase, is good for long crystal ingot, can reduce the alpha
Precipitation of Fe.
Lots of microstructure observation showed that in the department of sintered ndfeb alloy microstructure has the following characteristics: (
The matrix phase (
The main phase)
Grain is polygon;
Rich B phase exist in isolation block or granular;
Rich Nd down grain boundary or grain boundary coupling distribution;
In addition in the matrix and other impurities, oxide and empty, etc.