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

Abstract 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 Nd 2 Fe 14 B 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 °C is frequently equivalent to the heat treatment at a certain elevated temperature T eff >30 °C. The composition of phases in the studied NdFeB-based alloy after HPT corresponds to the state at T eff ~1140 °C.