Title :
Metastable A1 phase in Al-doped Nd-Fe-B magnets
Author :
Politano, R. ; Nozières, J.P. ; de la Bâthie, R. Perrier ; Missell, F.P.
Author_Institution :
Inst. de Fisica, Sao Paulo Univ., Brazil
fDate :
11/1/1993 12:00:00 AM
Abstract :
The role of metastable A1 phase in the coercivity of Al-doped Nd-Fe-B magnets is investigated in a magnet enriched in both Nd and Al. The as-sintered magnet (intrinsic coercive field iH c=3.6 kOe) contains an additional phase with Curie temperature Tc=180°C, while the annealed (600°C/1 h) magnet (iHc=12.1 kOe) does not. As-cast ternary alloys with compositions Nd-(20-x)at.%Fe-xat.%Al(x=1-10) show the metastable A1 phase with reduced Tc, but annealed alloys show the μ and δ phases of the Nd-Fe-Al system. Quaternary Nd-Fe-Al alloys are also studied. The disappearance of the ferromagnetic phase with Tc=180°C is associated with the decomposition of A1. The magnetic properties of δ are discussed, and the transformation kinetics of A1 are studied
Keywords :
Curie temperature; aluminium alloys; annealing; boron alloys; coercive force; ferromagnetic properties of substances; iron alloys; neodymium alloys; permanent magnets; solid-state phase transformations; δ phases; μ-phase; 1 hour; 180 degC; 600 degC; Al-doped Nd-Fe-B magnets; Curie temperature; Nd-Fe-B-Al; annealed magnet; as-sintered magnet; coercivity; decomposition; ferromagnetic phase; magnetic properties; metastable A1 phase; quarternary phase; ternary alloys; transformation kinetics; Annealing; Magnetic properties; Magnetization; Magnetometers; Magnets; Metastasis; Neodymium; Paramagnetic materials; Superconducting coils; Temperature;
Journal_Title :
Magnetics, IEEE Transactions on
