Synthesis of bulk nanostructured DO ₂₂ superlattice of Ni ₃ (Mo, Nb) with high strength, high ductility, and high thermal stability

We show that a bulk nanostructured material combining high strength, high ductility, and high thermal stability can be synthesized in a Ni-Mo-Nb alloy with composition approaching Ni ₃(Mo, Nb). By means of a simple aging treatment at 700°C, the grains of the parent face-centered cubic phase are made to transform into nanosized ordered crystals with DO ₂₂ superlattice maintaining a size of 10-20nm after up to 100 hours of aging and corresponding room-temperature yield strength of 820MPa and tensile ductility of 35. Deformation of the superlattice is found to predominantly occur by twinning on { 111 } planes of the parent phase. It is concluded that, although the respective slip systems are suppressed, most of the twinning systems are preserved in the DO ₂₂ superlattice enhancing the ductility.