Property investigation of the REM-Co and REM-Fe-B alloy powders obtained by means of hydrogenous embrittlement and the permanent magnets on their basis

Abstract

Abstracts. Different in chemical composition alloy Sm-Fe-Cu-Zr-CO, Sm-Gd-Er-Co-FeCu-Zr H Nd-Fe-Tb-B, Td-Fe-Tb-Cts-33 ingots were dispersed by combination of hydrogenous embrittlement and grind in ball-*rational mill as well as by breaking in highly intense disintegrator. It is shown that the hydrogenous embrittlement process can be controlled and there exists a principle ability to obtain powders with a specified granulometric composition. The powder obtained by hydrogenous embrittlement was compacted and fritted according to a certain program. The magnets obtained in such a way have more high properties than the magnets obtained by usual vibrational grinding. Statement of problem.The alloy ingot breakage is one of the most important step in the permanent magnet production process on the basis of rare-earth metals (REM)-Co and REM-Fe-By because the magnetic and structural properties of the powders determine the properties of the fiitted magnets. The traditional breakage method in the permanent magnet production is grinding in a vibrational ball mill. The method has certain hardly eliminable defects: significant plastic deformation, particle surface amorphization and relatively high oxidation level of powder particles.It is known the hydrogen absorption by metals is accompanied with a fragility increase [l]. The hydrogenation-dehydrogenation processes were studied on an instance of three-component alloy REM-Cos, REM-Col7 and REM-Fe-B with composition both stochiometric Nd2Fel4BY and Ndl5Fe77Bg [ 1,2,3,4,5-81. All alloys mentioned absorbs hydrogen well at a normal temperature and different hydrogen pressure. The saturation becomes at the pressure more 100 MPa. The entire process takes 1.. .2 hours. To accelerate the process the activation is required. Depending the process condition hydrides with different hydrogen content could be obtained: from x=2,7-4 (for NdZFel4B) to x=29 mass.% (for Ndl~Fe77B8).The hydrogen could be removed from the hydrogenated alloys at vacuum heating to 473 ... 673 K [3-61. The dehydrogenation consists of two stages: the most hydrogen amount is removed from the matrix phase NdzFel4B in the temperature interval 423 ... 523 K; the smallest hydrogen amount is removed at 623.. .923 K from the phase, enriched by neodymium [8]. The same work demonstrated the alloy spalling proceeds along the intergranular phase, enriched by neodymium. Along with hydrogen content increase the powder magnetization raises on 6.. .lo% and the anisotropy field simultaneously hardly reduces. From the analysis of Moess-Bauer spectra the authors [9] makes a conclusion on breaking of iron atom local environment and correspondingly on alpha-iron cluster formation. It was disclosed simultaneously [6] a significant increase of Curie temperature. Methods.The alloys were made in an inductive stove in the argon atmosphere. The alloy hydrogenation was performed at normal temperature and hydrogen pressure 1,2.. . 13 MPa. All samples undergoes the activation by means of vacuum heating before hydrogenation. The grind was processed...