Metastable states in R2Fe14B-based alloys processed by severe plastic deformation

The influence of severe plastic torsion straining (SPTS) under high pressur e on microstructure, phase composition and coercivity of cast sub-, super- and stoichiometric R2Fe14B (R = Nd, Pr)-based alloys was investigated. Defo rmation results in the formation of a metastable state characterised by ult rafine-grained (UFG) structure and non-equilibrium phase composition. Annea ling at 600 degrees C leads to complete or partial restoration of the initi al phase composition depending on the alloy composition. Due to SPTS and su bsequent annealing of the Pr20Fe73.5B5Cu1.(5) alloy, the formation of high coercivity UFG state with H-j(c) up to 2240 kA/m is observed. (C) 1999 Else vier Science B.V. All rights reserved.