Formation of two amorphous phases in the Ni60Nb18Y22 alloy after high pressure torsion

Abstract

It has been demonstrated for the first time that severe plastic deformation (SPD) permits to produce the metallic alloys containing two coexisting amorphous phases from the crystalline multiphase alloy. The as-cast Ni60Nb18Y22 alloy was coarse-grained and contained mainly NiY phase (grain size 25 µm) and also NbNi3 ,N i2Y, Ni7Y2 and Ni3Y phases (grain size 3–5 µm). High pressure torsion (4 GPa, 10 torsions) completely changed the structure. The sample after SPD contained two glassy phases and two other nanocrystalline NiY and Nb15Ni2 phases (grain size about 20 nm). The coarse-grained alloy was mainly ferromagnetic with a small paramagnetic component. After SPD the alloy becomes strongly diamagnetic with a small ferromagnetic component. Therefore, it has been revealed that severe plastic deformation allows one to produce the composite amorphous alloys. K e y w o r d s : severe plastic deformation, Y-Ni-Nb alloys, amorphous phases