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AM: Magnetismus

AM 8: Dauermagnetische Werkstoffe und Legierungen

AM 8.4: Vortrag

Dienstag, 27. März 2001, 12:15–12:30, S 5.4

Metastable borides and the inducement of texture in Pr₂Fe₁₄B-type magnets produced by HDDR — •O. Gutfleisch¹, A. Teresiak¹, B. Gebel¹, K.-H. Müller¹, N.B. Cannesan², D. Brown², and I.R. Harris² — ¹IFW Dresden, Institute of Metallic Materials, POB 270016, 01171 Dresden — ²School of Metallurgy and Materials, University of Birmingham, Birmingham B15 2TT, UK

The hydrogenation-disproportionation-desorption-recombination (HDDR) process is well established as a method for the production of highly coercive Nd₂Fe₁₄B magnets. Here, a modified HDDR process has been applied to Pr₂(Fe,Co,Zr)₁₄B-type alloys. XRD and Rietveld analysis show that a Fe₃B phase observed in a Pr_13.7Fe_80.3B₆ alloy solid-disproportionated at 875^o is transformed to Fe₂B and bcc Fe on further hydrogen annealing and that the formation of Fe₃B is partly suppressed when the alloy is processed at 800^o. No residual 2-14-1-type phases are observed after disproportionation of Pr_13.7Fe_63.5Co_16.7Zr_0.1B₆ alloy but here a new intermediate boride phase, Pr(Fe,Co)₁₂B₆ (rhombohedral R3m), is found. Pr(Fe,Co)₁₂B6 transforms to (Fe,Co)₂B and α-(Fe,Co) on further hydrogen annealing or conventional disproportionation. For both alloys it is found that processing at higher temperature leads to a better texture on recombination. The role of the Co and Zr additives is not primarily the stabilization of the 2-14-1 matrix phase against hydrogen disproportionation but more importantly the stabilization of intermediate boride phases.