Texture Formation Mechanism Of SmCo₇-based Bulk Nanocrystalline Magnet

SmCo₇-based nanocrystalline permanent magnetic materials have attracted much attention due to its wide application prospect,especially its low coercivity temperature coefficient,which makes it have great advantages in the field of high temperature application.Unfortunately,the reported SmCo₇-based nanocrystalline magnets are mostly isotropic bulk or ribbons,these magnets are not nearly as good as bulk with the texture in performance and application.There are also a few reports on the bulk SmCo₇-based magnets with the texture,the texture of these magnets are relatively weak and there is much room for improvement.This shows that the texture formation of bulk SmCo₇-based nanocrystalline magnets is a great challenge.Because the stability of SmCo₇ becomes worse when the grain size is too large,when the size is reduced to obtain stable SmCo₇,making texture at the nanometer scale is difficult.Therefore,understanding the texture formation mechanism of SmCo₇-based nanocrystalline magnets is of great significance for the development of high-performance magnets.In the present work,the following research work was carried out on the texture formation mechanism of SmCo₇ bulk nanocrystalline magnets by XRD,TEM and VSM.Starting from the study of the texture formation mechanism of single-phase SmCo₇nanocrystalline magnets,the high pressure thermal compression magnets and isostatic pressure magnets were analyzed,revealing that the texture formation of SmCo₇ is affected by uniaxial stress,axial compressive strain and vertical axial tensile strain.Combined with the calculation of surface energy and strain energy density,the results show that the texture formation of single phase SmCo₇ nanocrystalline is due to the anisotropy of the strain energy density along in different directions for newly generated nanocrystalline under the action of large stress,axial compressive strain and vertical axial tensile strain during the amorphous crystallization process,the anisotropy is enlarged by large stress and large strain,and the preferentially grow of the low energy plane.And the effect of deformation amount on the texture of SmCo₇ nanocrystalline magnets was also studied.The texture formation mechanism of SmCo₇/Fe（Co）composite nanocrystalline magnets was investigated,and the effects of soft phase content,precursor state and deformation amount on the texture of nanocrystalline magnets were studied.The results show that the texture formation mechanism of SmCo₇/Fe（Co）composite nanocrystalline magnets is the same as that of single phase,and the addition of soft magnetic phase weaken the texture of nanocrystalline composite magnets.By studying the precursor,the results show that the hard magnetic phase complete amorphous precursor is more conducive to the formation of the texture,and with the increase of strain,the texture of the composite nanocrystalline magnet show a trend of strengthening.