Abstract
Optimizing fabrication parameters for rapid solidification of Re-Fe-B (Re = Rare earth) alloys can lead to nanocrystalline products with hard magnetic properties without any heat-treatment. In this work, we enhanced the magnetic properties of Ce17Fe78B6 ribbons by engineering both the microstructure and volume fraction of the Ce2Fe14B phase through optimization of the chamber pressure and the wheel speed necessary for quenching the liquid. We explored the relationship between these two parameters (chamber pressure and wheel speed), and proposed an approach to identifying the experimental conditions most likely to yield homogenous microstructure and reproducible magnetic properties. Optimized experimental conditions resulted in a microstructure with homogeneously dispersed Ce2Fe14B and CeFe2 nanocrystals. The best magnetic properties were obtained at a chamber pressure of 0.05 MPa and a wheel speed of 15 m·s−1. Without the conventional heat-treatment that is usually required, key magnetic properties were maximized by optimization processing parameters in rapid solidification of magnetic materials in a cost-effective manner.
Highlights
Re2 Fe14 B-type permanent magnets (Re = rare earth metals) are essential components in many electric machines and have been widely-used in various fields due to their outstanding hard magnetic properties [1,2]
We investigated the effects of fabrication parameters on both microstructure and magnetic properties of Ce17 Fe78 B6 ribbons produced by a new direct method without heat-treatment
Using Ce17 Fe78 B6 alloys that had been fabricated by quenching without subsequent heattreatment, we investigated the effects of chamber pressure and wheel speed on microstructure and magnetic properties
Summary
The rapid solidification technique of melt-spinning, with cooling rates up to 104 –106 K·s−1 , is one of the most important techniques for producing Re-Fe-B alloys with homogeneous nanostructure and desirable hard magnetic properties [3]. In this process, molten alloy is ejected onto a rotating metal chill (or wheel) of much larger thermal mass and rapidly quenched to produce thin ribbons, typically a few centimeters wide and a few microns thick. When the wheel speed is lower than an optimum wheel speed (i.e., under-quenched condition), inhomogeneous microstructure may form. The melt-spinning, is probably not Materials 2017, 10, 869; doi:10.3390/ma10080869 www.mdpi.com/journal/materials
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