Title :
Magnetization versus heat treatment in rapidly solidified NdFeB alloys
Author :
Clavaguera-Mora, M.T. ; Baro, M.D. ; Surinch, S. ; Diego, J.A. ; Clavaguera, N.
Author_Institution :
Dept. de Fisica, Univ. Autonoma de Barcelona, Spain
fDate :
9/1/1990 12:00:00 AM
Abstract :
NdFeB melt-spun amorphous or partially amorphous alloys of four compositions were prepared. Their crystallization kinetics induced by thermal treatment was studied by differential scanning calorimetry and scanning and transmission electron microscopy. Scanning electron microscopy demonstrated that heterogeneous nucleation occurs preferentially at the ribbon surface which was in contact with the wheel. The explicit form of the kinetic equation that best describes the first stage of crystallization under high undercooling conditions was obtained for each alloy. From the crystallization results, the lower part of the experimental time-temperature-transformation curves was deduced for each alloy and extrapolated up to the high-temperature limit of their validity. Microstructural observations showed a typical size of the microcrystals obtained by heat treatment of ~100 nm. From the magnetic properties measured with a vibrating sample magnetometer, the same magnetic behavior of partially crystallized alloys is observed regardless of the temperature of annealing provided the same crystallization fraction, x, is achieved, at least for small values of x (typically ~10%)
Keywords :
annealing; boron alloys; crystallisation; ferromagnetic properties of substances; iron alloys; magnetic properties of amorphous substances; magnetisation; neodymium alloys; scanning electron microscope examination of materials; thermal analysis; transmission electron microscope examination of materials; NdFeB alloys; amorphous; annealing; crystallization kinetics; differential scanning calorimetry; heat treatment; heterogeneous nucleation; high undercooling conditions; kinetic equation; magnetic properties; magnetization; melt-spun; microcrystals; partially amorphous alloys; rapidly solidified; scanning electron microscopy; thermal treatment; transmission electron microscopy; Amorphous materials; Calorimetry; Crystallization; Heat treatment; Kinetic theory; Magnetization; Scanning electron microscopy; Surface treatment; Transmission electron microscopy; Wheels;
Journal_Title :
Magnetics, IEEE Transactions on