Title :
Ageing effects in sintered (Nd,Dy)15(Fe,Co,Mo,Al)77 B8 permanent magnets
Author :
Eckert, D. ; Müller, K.H. ; Wolf, M. ; Rodewald, W. ; Wall, B.
Author_Institution :
Inst. fuer Festkorper- und Werkstofforschung Dresden, Germany
fDate :
11/1/1993 12:00:00 AM
Abstract :
The effect of annealing on the coercivity jHc of sintered Nd-Fe-B is contradictorily discussed in literature, jHc depends on annealing temperature TA, annealing time, cooling rate, and details of the chemical composition. In the case of (Nd,Dy)15(Fe,Co,Mo,Al)77B8 a decrease of jHc is observed for TA⩾450°C. Passing a strong minimum at TA=575°C and a maximum at TA≈800°C, jHc approaches its post-sintering value at higher annealing temperatures. Above the minimum, jHc varies practically reversibly if TA is increased or decreased. The ratio of coercivities measured after annealing at 750°C and 575°C increases with increasing measuring temperature and is more than 5 above 150°C. Analyzing the behavior of j Hc by jHc=cHA-Ne μ0-1J, it is found that c=0.43 for TA=750°C and c=0.29 for TA=575°C, but N e=1.4 is independent of TA
Keywords :
ageing; aluminium alloys; annealing; boron alloys; cobalt alloys; coercive force; dysprosium alloys; ferromagnetic properties of substances; iron alloys; molybdenum alloys; neodymium alloys; permanent magnets; sintering; (Nd,Dy)15(Fe,Co,Mo,Al)77B8; (NdDy)15(FeCoMoAl)77B8; 10 to 60 min; 350 to 1000 C; anisotropy field; annealing temperature; annealing time; chemical composition; coercivity; cooling rate; permanent magnets; sintered Nd-Fe-B; Aging; Anisotropic magnetoresistance; Annealing; Chemicals; Coercive force; Cooling; Heat treatment; Magnetic field measurement; Permanent magnets; Temperature dependence;
Journal_Title :
Magnetics, IEEE Transactions on
