A route for recycling Nd from Nd-Fe-B magnets using Cu melts

• Published in: Journal of alloys and compounds 2015-10, Vol.647, p.997-1006
• Main Authors: Moore, Martina, Gebert, Annett, Stoica, Mihai, Uhlemann, Margitta, Löser, Wolfgang
• Format: Article
• Language: English
• Subjects: A: Permanent magnets; B: Liquid–solid reactions; C: Microstructure; Copper; D: Scanning electron microscopy; Ferrous alloys; Magnetic materials; Magnets; Neodymium; Rare earth alloys and compounds; Recycling; Scrap; Separation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2015.05.238

Phase evolutions in Nd-Fe-B magnet/Cu systems have been explored with regard to Nd recycling. It was demonstrated that large scale phase separation into a ferromagnetic Fe(B)-rich ingot core with α-Fe main phase and a non-magnetic (Cu,Nd)-rich ingot rim takes place upon arc melting with Cu fractions ≥ 21.5 wt.-%. The re-solidification of the Nd2Fe14B magnet main phase is suppressed. The rim consists of the Cu2Nd main phase and CuNd/Cu4Nd minority phases in which Al traces from the magnetic material are gathered. Induction melting of such Nd-Fe-B/Cu mixtures can support the separation of these phase regions with very sharp boundaries. Main features of liquid phase separation and microstructure evolution have been interpreted on the basis of Nd-Fe-Cu phase diagram data. The key advantage with respect to Nd recycling from Nd-Fe-B permanent magnet scrap is the substantial accumulation of Nd in the (Cu,Nd)-rich region of the phase separated solidified specimen, which can be easily detached from the Fe-rich part by mechanical-magnetic treatments. Such portions contained up to ∼44 wt.-% Nd (25 at.-%) in first lab-scale experiments. Nd recovery from the (Cu,Nd)-rich fractions is possible by exploiting the large chemical property differences between the reactive rare earths elements and Cu. •phase evolution analysis in Nd-Fe-B magnet/Cu systems with regard to Nd recycling.•Cu ≥ 21 wt.-%, large scale phase separation- Fe(B)-rich ingot core, (Cu,Nd)-rich rim.•high Nd content (∼44 wt.-%) of (Cu,Nd)-rich region, mechanical-magnetic treatments.