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–12.3at% Nd–7.6 at% B alloy (5GPa, 1rpm, 5rot, 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 TSPD=30°C is frequently equivalent to the heat treatment at a certain elevated temperature Teff>30°C. The composition of phases in the studied NdFeB-based alloy after HPT corresponds to the state at Teff ~1140°C. •The NdFeB-based alloy amorphises under the action of severe plastic deformation (SPD).•The amorphous phase with embedded Nd2Fe14B nanocrystals is formed.•SPD at room temperature is equivalent to the annealing at Teff ~1140°C.•Teff depends on the composition of an alloy.