Study of the formation of crystal texture in α-Fe/Nd2Fe14B nanocomposite magnets prepared by controlled melt-spinning

Controllably Manipulating Three-Dimensional Hybrid Nanostructures for Bulk Nanocomposites with Large Energy Products

“…The lower E leads to the growth of the (00 l ) axis-aligned SmCo 7 crystal into a disc-shaped nanocrystal as observed in the nanostructure made at T d = 700 °C, which has also been reported in previous studies. , Strikingly, a large temperature gradient (Δ T = 170 °C/mm) obtained at T d = 630 °C (Figure b) is likely to facilitate the growth of the oriented crystals into the rod-shaped nanocrystals, as the large temperature gradient could overcome the energy barrier of surface energy increase for crystal growth, leading to a directional growth of the oriented nanocrystals (along the temperature gradient direction) and their texture development simultaneously. The temperature-gradient-induced texture growth has been reported in previous directional solidification and annealing studies. , These results suggest that the morphology of the oriented grains can be rationally tuned with the temperature gradient, which strongly correlates with the deformation temperature, deformation amount, and cooling rate in the deformation process (Figure b; Supporting Information), yielding a value of 170 °C/mm at T d = 630 °C. This temperature gradient (170 °C/mm) is likely to match well with the directional growth of oriented SmCo crystals, leading to the rod-shaped SmCo nanograins with a strong c -axis texture at T d = 630 °C.…”

Novel Bimorphological Anisotropic Bulk Nanocomposite Materials with High Energy Products

“…The use of high stress and large strain during temperature‐gradient deformation is the key to aligning the rod‐shaped SmCo 7 nanograins in our magnets. To elucidate the origin of SmCo 7 grain alignment, we examined four possible mechanisms that have been reported in other materials: surface energy minimization, stress (pressure) effect, strain‐energy anisotropy, and temperature gradient . Both the surface energy minimization and pressure effects were excluded by annealing SmCo‐based amorphous precursors under normal and high ( p = 5 GPa) pressures, respectively; in both cases, the resulting SmCo 7 grains were isotropic (Figures S4 and S8, Supporting Information).…”

Surface quality, microstructure and magnetic properties of Nd2(Fe,Zr,Co)14B/α-Fe alloys prepared by different melt-spinning equipments

“…Alloy ingots with nominal compositions of Nd 10 obtained by remelting the ingots and then spinning with roll speeds ranging from 15 to 25 m/s in an Ar atmosphere. The flux of alloy melt was 6 g/s.…”

“…Micromagnetic calculations [4][5][6] showed that the effective exchange coupling requires a fine-grained and homogeneous microstructure. Experimental results of previous studies [7][8][9][10] showed that the fabrication methods can greatly affect the microstructure and the magnetic properties of nanocomposite magnets. At present, meltspinning is a major method to prepare nanocomposite magnets.…”