| The Nd2Fe14B based alloy is the strongest hard magnetic material to date. In this thesis, a study of systematical heat treatments of NdFeB based melt-spun nanocomposite ribbons has been. Comparison has been made between samples treated by rapid thermal annealing and by furnace annealing. Magnetic hysteresis loops have been measured for all the samples by an alternating gradient magnetometer. It was found that magnetic hardening can be realized in annealing time as short as 1 second. Structural characterization was performed including X-ray diffraction, phase transition temperature measurement by differential thermal analysis, and microstructure observation by transmission electronic microscopy. The correlation between magnetic properties and annealing parameters has been investigated. It was revealed that the magnetic hardening is based on the amorphous-crystalline phase transition. The minor loops were also measured to study the coercivity mechanism of the annealed ribbons. |
