Abstract
The structural transformations and magnetic property changes of the Nd16.2FebalCo9.9Ga0.5B7.5 (SG1, SG2) and Nd15.0FebalGa2.0B7.3 (SG3) nanocomposite alloys obtained by melt spinning in the as-quenched state and after annealing at a temperature range of 560–650 °C for 30 min were studied. The methods used were X-ray diffraction analysis, magnetic property measurements, TEM studies, X-ray fluorescence analysis and Mössbauer spectroscopy. Amorphous phase and crystalline phase Nd2Fe14B (P42/mnm) were observed in the alloy after melt spinning. The content of the amorphous phase ranged from 20% to 50% and depended on the cooling rate. Annealing of the alloys resulted in amorphous phase crystallization into Nd2Fe14B and led to the increased coercivity of the alloys up to 1840 kA/m (23.1 kOe) at 600 °C annealing for 30 min. The alloy with the maximum coercivity had a grain size of the Nd2Fe14B phase ≈50–70 nm with an Nd-rich phase between grains.
Highlights
Permanent magnets have found their application in various engines, generators, recording and storage devices, etc
Particular interest is shown in nanocrystalline or nanocomposite permanent magnets obtained by high-energy methods: high-energy milling, severe plastic deformation, quenching from liquid state, etc
The amount of amorphous phase grew as the cooling rate increased
Summary
Permanent magnets have found their application in various engines, generators, recording and storage devices, etc. Particular interest is shown in nanocrystalline or nanocomposite permanent magnets obtained by high-energy methods: high-energy milling, severe plastic deformation, quenching from liquid state, etc In these systems, exchange coupling effects [4,5,6,7,8,9] or the formation of intergranular phases changing the exchange interaction between the grains and increasing the coercivity can be observed. Metals 2019, 9, 497 alloys obtained by the extreme effects methods, the magnetic properties are determined by the fundamental parameters of the phases but mainly by the parameters of the structure and morphology of these phases Another important question linked to the formation of a highly coercive state is the alloying of the Nd-Fe-B system. Nd-Fe-B-Ga nanocrystalline alloy, with the goal of clarifying an understanding of the relationship between the structure and properties of this system in the initial state and after the heat treatment
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