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The effect of casting method on the magnetic properties of Sm(Co0.63Fe0.28Cu0.07Zr0.02)7.6 magnet has been investigated. The results show that the plate-mold ingot (PM) and strip-casting flake (SC) have the same phase composition. Compared with PM, the SC has a smaller grain size and larger fine-grain region due to its larger degree of undercooling. The magnetic properties of the PM magnet are Br = 11.63 kG, Hcj = 25.65 kOe, (BH)max = 30.97 MGOe, while the magnetic properties of SC magnet are Br = 11.45 kG, Hcj = 24.00 kOe, (BH)max = 30.03 MGOe. The reason for the low remanence of the SC magnet is revealed by the XRD and EBSD results. It shows that the PM magnet has a better easy-axis orientation than the SC magnet, due to the existence of fine grains in SC that are unfavorable for the alignment under a magnetic field. [ABSTRACT FROM AUTHOR]

We achieved ultra-high coercivity of 5.65 kOe in L10-Mn1.33Ga alloy via the hot deformation (HD) method and revealed the hardening mechanism. Hot deformation led to recrystallization and grain refinement, where the average grain size was reduced to about 1.5 μm for HD-88% magnet. The coercivity mechanism indicated a weak pinning model by magnetic mini-loop analysis. It was found that small grains were formed, accompanied by a certain number of {111} ⟨11-2⟩ twins for HD magnets. The magnetic domain observation showed that both the sub-micro grain boundary and the twin boundary were acted as the pinning center of the domain wall, but the latter had weaker pinning effect. The ultra-high coercivity of the HD-88% Mn1.33Ga magnet originated mainly from the pinning of the grain boundary enhanced by grain refinement. Further grain refinement and twin structure inhibition will be promising approaches in order to obtain higher magnetic properties for L10-MnxGa bulk magnets. [ABSTRACT FROM AUTHOR]

Phase and texture evolution of the hot-deformed Sm(Co,Fe,Cu,Zr)z magnet prepared by spark plasma sintering (SPS) have been investigated. The effects of hot deformation temperature and height reduction on the phase structure and magnetic properties of the magnet were studied. The results show that with 90% height reduction at 900 °C, the hot-deformed magnet with TbCu7 structure obtains an obvious $c$ -axis texture. However, with increasing hot deformation temperature, some 1:7H phases decompose into 2:17R, 1:5H, and Zr-rich particle phases in the hot deformation process. The hot-deformed magnet with 85% height reduction possesses a remanence ($M_{r}$) of 6.9 kG, which is higher than that of the isotopic precursor. [ABSTRACT FROM AUTHOR]

The Sm(CobalFe0.28Cu0.07Zr0.03)7.6 magnets were made by a casting process with two different cooling rates. X-ray diffraction analysis shows that the main phase of the two as-cast alloys consist of 1:5, 1:7, and 2:17 (hexagonal) phase. While a few of rhombohedral 2:17 phases appear in the ingots with the lower cooling rate. The electron probe micro-analysis and corresponding wavelength dispersive x-ray results indicate that a higher cooling rate of the as-cast alloy is helpful to the uniformity of Cu element distribution in the ingots and magnets, especially for suppressing the formation of 2:17 R phase in ingots. The coercivity and squareness of magnet prepared from ingot with higher cooling rate increase by 72 and 48 percentage, respectively. The microstructure observation shows that some cell boundaries are destroyed in the magnet made by lower cooling rate, while the cell boundaries are well developed in the magnet made by higher cooling rate. [ABSTRACT FROM AUTHOR]

The correlation between microstructure and magnetic properties of 2:17 SmCo commercial magnets 32 H and 32 L is studied. The 32 H magnet with high coercivity has an excellent ($00l$) orientation texture, and its magnetic properties are (BH) $_{\mathrm {max}}= 29.47$ MGOe, $B_{\mathrm {r}} = 11.20$ kG, and $H_{\mathrm {cj}} = 29.45$ kOe. The magnetic properties of the 32 L magnet with low coercivity are (BH) $_{\mathrm {max}}= 29.28$ MGOe, $B_{\mathrm {r}} = 11.40$ kG, and $H_{\mathrm {cj}} = 9.829$ kOe. The electron probe microanalysis results show that a Cu-lean grain boundary region is obvious in the 32 H magnet, which affects the squareness of the demagnetization curve. The transmission electron microscope result shows that the cell size and cell boundary thickness of high and low coercivity magnets are 129.32 and 9.83, and 90.94 and 7.87 nm, respectively. But the cell structure of the 32 H magnet is more complete and clearer than that of the 32 L magnet. The difference of the Cu concentration between the cell boundary phase and cell phase in the 32 H magnet is bigger than that of the 32 L magnet, which is really responsible for the high coercivity. [ABSTRACT FROM AUTHOR]

Highlights • Sintered Nd-Fe-B strip casting flakes (SC) and waste sintered magnets (SM) show the approximate HD process, which accelerates with increasing pressure. • The surface activation process accelerates with increasing pressure, and almost disappears when the initial hydrogen pressure reaches to 6 MPa. • The hydrogen content of SM is lower than SC, and increases with increasing pressure. • For the SM, blasting power of HD process decreases with the increase of the initial hydrogen pressure. Abstract Hydrogen treatment technology is developed to recycle the waste Nd-Fe-B sintered magnets in the way of short route, low cost, and high efficiency. In present study, effect of hydrogen pressure on hydrogen decrepitation (HD) process of sintered Nd-Fe-B strip casting flakes (SC) and waste sintered magnets (SM) was systematically studied. Both SC and SM show the approximate HD process, which accelerates with increasing pressure. The surface activation process accelerates with increasing pressure, and almost disappears when the initial hydrogen pressure reaches to 6 MPa. The hydrogen content of SM is lower than SC, and increases with increasing pressure. For the SM, blasting power of HD process decreases with the increase of the initial hydrogen pressure. It provides beneficial reference for recycling waste Nd-Fe-B sintered magnets. [ABSTRACT FROM AUTHOR]

PrCo5 magnet can have excellent magnetic properties and good thermal stability. In this paper, anisotropic nanograin PrCo5 hot deformed magnets with and without PrCu eutectic alloy were prepared by the spark plasma sintering technique. For the 70% hot deformed magnet with 6 wt.% PrCu, the coercivity of the magnet achieves 10.1 kOe, and is increased to be 14.6 kOe after annealed at 550°C, more than twice that of the undoped magnet (6.7 kOe). The nonmagnetic PrCu phase is mainly distributed in the interface of the grains, introducing a demagnetization coupling effect among the hard magnetic grains, resulting in large enhancement of the coercivity. [ABSTRACT FROM AUTHOR]

Commercial NdFeB powders mixed with DyH x nanoparticles are hot pressed and hot deformed into anisotropic magnets by Spark Plasma Sintering (SPS). The hot deformed magnet exhibits strong c -axis crystallographic texture. The coercivity of the magnet doped with 1.0 wt% DyH x is increased by 66.7%, compared with the magnet without DyH x , while the remanence decreases only by 3%. TEM observation shows that there exists a continuous (Nd,Dy) 2 Fe 14 B layer between Nd-rich phase and NdFeB main phase. [ABSTRACT FROM AUTHOR]