The main raw materials of NdFeB permanent magnets are rare earth metal lanthanum, metallic elemental iron and non-metallic element boron (sometimes added with aluminum, cobalt, lanthanum, cerium, lanthanum, gallium, etc.). The general expression is: RE2TM14B (RE=Nd, Pr, DyTM=Fe, Co), NdFeB ternary permanent magnet material is based on Nd2Fe14B compound, and its composition should be similar to that of compound Nd2Fe14B. However, when the ratio of Nd2Fe14B is completely divided, the magnetic properties of the magnet are very low, even non-magnetic, except that the content of bismuth and boron in the actual magnet is larger than that of the Nd2Fe14B compound (ie, the yttrium-rich phase and the boron-rich phase are formed). In order to obtain better permanent magnet performance.
This phase is the main phase of the magnet, and its volume percentage (which has been substantially fixed after the ingot has been refined) determines the remanence (Br) of the magnet. The maximum magnetic energy product ((BH)m), and the magnetic field orientation during molding is to achieve its arrangement so that the easy magnetization axis (C) of this molecular structure is arranged in the orientation direction, thereby achieving higher magnetic properties.
Rich B phase
The B-rich phase exists as a certain compound in the matrix, which is a non-magnetic phase, which is generally detrimental to magnetic properties, but the presence of a B-rich phase causes the ingot to be easily broken.
Rich Nd phase
The presence of the Nd-rich phase is mostly present in the Nd-Fe compound, which plays an important role in increasing the density of the magnet during sintering. Because of its very active nature, it is easily oxidized to form an oxide phase, which is very detrimental to the corrosion resistance of the magnet. However, when the Nd-rich phase is relatively large, it is advantageous for the long crystal of the steel ingot, and the precipitation of α-Fe can be reduced.