0000000000297455
AUTHOR
A. A. Zhuravlyev
Post-sintering heat treatment effect on the coercivity of sintered (Nd,Dy)15(Fe,Co,Mo,Al)77B8 permanent magnets
Abstract The effect of heat treatment on the intrinsic coercivity, iHc and microstructure were investigated for sintered (Nd,Dy)15(Fe,Co,Mo,Al)77 B8 permanent magnet. The microstructure has been investigated by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray spectroscopy and Mossbauer spectroscopy. The observed behaviour of iHc may be caused by a superposition of the following effects: (i) the distribution of the nonmagnetic phases and the ratio of the amount of hard magnetic Nd2Fe14B-phase to the amount of the residual phases; (ii) homogeneous distribution of elements in the main phases; (iii) removing the stresses in the phases; and (iv) diffusion of Al, …
ANNEALING EFFECT ON COERCIVITY AND MICROHARDNESS IN SINTERED (Nd, Tb)15(Fe, Co, Al)78B7 MAGNETS
The variation of the coercivity and microhardness with annealing (475–1150°C/3.6 ks) of sintered (Nd, Tb) 15 (Fe, Co, Al) 78 B 7 permanent magnet have been investigated. The data indicate that the coercivity reaches the mininum and the maximum at 600°C and 775°C, respectively. Optical and scanning electron microscopy and magnetic domain structure observations give no hints to any change in microstructure. Fitting of the Mössbauer spectra of permanent magnets for different coercivity ( i H c ) values revealed that magnetic hyperfine fields (B Hf ) on all Fe sites are reduced with the increase in i H c value and the higher value of the i H c corresponds to the higher value of the Mössbauer l…
The effect of less additives on magnetic properties and microstructure of sintered Nd–(Fe,Ti,Al)–B magnets
Abstract The effect of the addition of 0.5 at.% Cu, Ga, Hf, V, Mo, Nb, Co, Ni, Cr, Dy or Tb on the magnetic properties and the microstructure of sintered Nd 16 Fe 75.22 Ti 1.26 Al 0.32 B 7.2 magnets has been studied. It is shown that these additives cause a small decrease in remanence and in intrinsic coercivity, with the exception of Cu, Dy and Tb additives, which lead to an increase in the intrinsic coercivity. The correlation between the hyperfine magnetic field and the magnetic properties of the investigated magnets is discussed.
Peculiarities of Forming of Magnetic Hardening in Sintered Nd15Fe76.2Ti1.0Al0.8B7 Permanent Magnet by Ageing
Variations of the intrinsic coercivity ( i H c ) with ageing (at 293 to 1173 K for 0.45 to 57.6 ks) of sintered Nd 15 Fe 76.2 Ti 1.0 Al 0.8 B 7 have been investigated. The tests indicated minimum and maximum of intrinsic coercivity ( i H min c and i H max c ) at temperatures 725 K and 1025 K, respectively. The observed behaviour of i H c has been compared with microhardness measurements and microstructure observations (SEM, EDAX, domain structure (DS) and room temperature Mossbauer spectroscopy). SEM and DS investigations gave hints to a change in microstructure. Fitting of the Mossbauer spectra of permanent magnets for different i H c has shown that the magnetic hyperfine field Bhf of 8j2 …