Search

Abstract Stress-induced alignment of Nd 2 Fe 14 B nanograins along (001) planes represents a practical process with which to create uniaxial high-anisotropy Nd Fe B magnetic materials. The residual non-oriented coarse-grain defect at ribbons' surfaces not only deteriorates the [001]-oriented structure but also facilitates the low-field nucleation of reversed magnetic domains. Although the local structural defect has proved to be controllable via doping refractory ceramic nanomaterials, the natures of coarse-grain suppression and corresponding magnetic configuration variation remain poorly known. Herein, we comprehensively discuss the correlation between structures and magnetic configurations to address the role of WC dopants in the kinetics of stress-induced deformation system. The statistical data suggest that the reinforced stress caused by WC nanoparticles effectively suppresses the size of Nd 2 Fe 14 B grains and induces their anisotropic growth. Simultaneously, the evolved (006) polar figures further confirm that the crystallographic orientation of interfacial Nd 2 Fe 14 B grains is also improved by reinforced stress. The analysis for magnetic configurations around dopants confirms that the coarse-grain inhibited structure reduces the low-field nucleation probability of reversed magnetic domains. Relying on their combined effect, the coercivity is increased by about 12%. These observations are further verified by the micromagnetic simulation computations. All these above findings may enrich the knowledge of stress-induced deformation mechanism and deepen the fundamental understanding of the correlation between structure and magnetic features. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A Dy-Cu eutectic injection process accompanying by hot deformation had the potential to fabricate the high-performance die-upset magnets. The good fluidity of Dy-Cu eutectic liquid accelerated the formation of near-surface texture and suppressed largely the grain growth during subsequent heat treatment. By the high-temperature microstructure evolution, the maximum energy product of injected magnets was substantially increased by 17.8%, from 45 to 53 MGOe. The near-surface microstructure of injected magnets was studied to clarify the effect of inhomogeneous Dy-Cu distribution on the texture and grain size. [ABSTRACT FROM AUTHOR]

The microstructure of ribbons interface was optimized by doping the hexagonal boron nitride nanoplatelets (h-BNNP) in hot-deformed magnets. The remanence increased markedly and reached to a maximum value of 14.06 kGs. The coercivity and the energy product exhibited similar variation trends to the remanence, showing maxima of 16.92 kOe and 49 MGOe, respectively. Microscopy observations revealed that surface grains of ribbons tended to align with the interior grains due to the uniform local compressive stress induced by h-BNNP with relatively large flat surface, resulting in hot-deformed magnets with microscopically homogeneous structure and improved texture. [ABSTRACT FROM AUTHOR]

Anisotropic Nd-Fe-B magnets with WC addition were prepared by hot deformation process. The effect of WC addition on the compressive and bending strength of hot-deformed Nd-Fe-B magnets has been investigated. The results suggest that the mechanical properties of hot-deformed magnets without WC addition show distinct anisotropy. Meanwhile, WC addition lowers the mechanical anisotropy in two directions parallel and perpendicular to c -axis, especially the compressive strength. The optimum mechanical properties are obtained at 1.0 wt % WC addition without sacrificing the magnetic properties. The observation for microstructure reveals that the fracture mechanism of hot-deformed magnets is a typical intergranular fracture and the crack is prior to propagate along the ribbon boundary. The improved mechanical properties might be attributed to both the grain refinement at ribbon boundaries and the reinforced effect of WC addition. [ABSTRACT FROM AUTHOR]

HDDR processed Nd-Fe-B powders blended with Nd-Cu powders were hot-pressed and then hot-deformed to obtain fully dense, anisotropic magnets. The microstructure evolution in hot-pressed and hot-deformed HDDR magnets was studied to illustrate the impact of Nd-Cu diffusion on coercivity and deformation ability. It was found that the coercivity and the deformation ability were improved significantly by Nd-Cu addition. The coercivity of hot-deformed magnets was increased from 3.81 kOe to 13.01 kOe after 2 wt% Nd-Cu additions and the annealing at 900 °C for 2 h. Scanning electron microscopy and transmission electron microscopy observations revealed that the variation in coercivity was attributed to the diffusion of Nd-Cu along the grain boundaries during hot pressing and hot deformation. [ABSTRACT FROM AUTHOR]

Anisotropic ultrafine-grained Nd-Fe-B magnets with WC addition were prepared by hot deformation. With WC nano-particles addition of ~ 1.0 wt.%, the squareness was optimized and the coercivity of the hot-deformed magnets increased substantially by 2.16 kOe, from 15.59 to 17.75 kOe without expense of the remanent magnetization. The observation for microstructure revealed that the WC nano-particles mainly existed on the interfaces of melt-spun ribbons. Meanwhile, due to the local compressive stress induced by the hard WC nano-particles, the deformability of neighboring grains was remarkably enhanced which leads to the reduction of the coarse grain regions. [ABSTRACT FROM AUTHOR]