Amorphization of crystalline phases in the Nd-Fe-B alloy driven by the high-pressure torsion

High pressure torsion (HPT) has been used for the severe plastic deformation (SPD) treatment of molten Fe-12.3 at% Nd-7.6 at% B alloy (5 GPa, 1 rpm, 5 rot, room temperature). After HPT the microstructure contained the nanograins of the ferromagnetic Nd2Fe14B phase embedded in the amorphous matrix with uniform composition. It is different to the commercial multicomponent FeNdB-based alloy where two different amorphous phases appeared after HPT (B.B. Straumal, A.R. Kilmametov, A.A. Mazilkin, S.G. Protasova, K.I. Kolesnikova, P.B. Straumal, B. Baretzky, Mater. Lett., 2015, 145, pp. 63-66). The SPD-treatment at room temperature T-SPD=30 degrees C is frequently equivalent to the heat treatment at a certain elevated temperature T-eff > 30 degrees C. The composition of phases in the studied NdFeB-based alloy after HPT corresponds to the state at T-eff similar to 1140 degrees C. (C) 2015 Elsevier B.V. All rights reserved.