Metastable borides and the inducement of texture in Pr2Fe14B-type magnets produced by HDDR

A modified hydrogenation-disproportionation-desorption-recombination (HDDR) process has been applied to Pr-2(Fe, Co, Zr)(14)B-type alloys. XRD and Rie tveld analysis show that a Fe3B phase observed in a Pr13.7Fe80.3B6 alloy so lid-disproportionated at 875 degreesC is transformed to Fe2B and bee Fe on further hydrogen annealing and that the formation of Fe3B is partly suppres sed when the alloy is processed at 800 degreesC. No residual 2-14-1-type ph ases are observed after disproportionation of Pr13.7Fe63.5Co16.7Zr0.1B6 all oy but here a new intermediate boride phase, Pr(Fe, Co)(12)B-6 (rhombohedra l (R) over bar 3m), is found. Pr(Fe, Co)(12)B-6 transforms to (Fe, Co)(2)B and alpha-(Fe, Co) on further hydrogen annealing or conventional disproport ionation. 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 addi tives is not primarily the stabilization of the 2-14-1 matrix phase against hydrogen disproportionation but more importantly the stabilization of inte rmediate boride phases.