Structural and phase transitions in the amorphous and nanocrystalline Ti50Ni25Cu25 alloys upon high-pressure torsion

The evolution of the structure and phase composition upon room temperature high-pressure torsion of the amorphous and nanocrystalline Ti50Ni25Cu25 alloy has been studied. It is shown that the accumulation of deformation regardless of the initial state of the alloy leads to the occurrence of cyclic «amorphous state⇒crystal» and «crystal⇒amorphous state» phase transformations. After the application of only hydrostatic pressure, without torsion, to the initially amorphous Ti50Ni25Cu25 alloy, a small amount of crystalline phase is present in the structure. The observed features of the structural transformations are explained in terms of the dissipation of mechanical energy, which is continuously introduced into the solids upon high-pressure torsion. [Display omitted] •Cyclic phase transformations of the Ti50Ni25Cu25 alloy upon HPT.•Hydrostatic pressure gives rise to nanocrystallization of the Ti50Ni25Cu25 amorphous alloy.•Suppression of the B2⇒B19 thermoelastic martensitic transformation in nanocrystals.•Dissipation of mechanical energy in a solids upon severe plastic deformation.