Amorphization of Nd–Fe–B alloy under the action of high-pressure torsion

highlights
• The NdFeB-based alloy amorphises under the action of severe plastic deformation.
• Such amorphisation has been observed for the first time.
• Mixture of two different amorphous phases with embedded nanocrystals is formed.
• One amorphous phase is Fe-rich, another is Nd-rich.

The high pressure torsion (HPT) has been used for the severe plastic deformation (SPD) treatment of liquid-phase sintered hard magnetic NdFeB-based alloy (5 GPa, 1 rpm, 5 torsions, ambient temperature). The amorphization of the crystalline alloy under the action of HPT has been observed. HPT permitted to obtain for the first time the mixture of two different amorphous phases with embedded grains of the ferromagnetic Nd2Fe14B phase. The SPD-treatment at ambient temperature TSPD=300 K is frequently equivalent to the heat treatment at a certain elevated temperature Teff>300 K. The composition of phases in the studied NdFeB-based alloy after HPT corresponds to the state at Teff~1170 °C.