This work reveals a new method to generate nano-twinned structure via a hexagonal-close-packed (hcp) to face-centered-cubic (fcc) phase transformation coupled with grain growth in nanocrystalline Co-Ni alloys prepared by pulse electrodeposition. This nano-twinned structure (with lamellar width of about 30 nm within grains of 300 nm in size) in the form of high temperature fcc phase demonstrates an extraordinary stability that the structure remains at 4.2 K and 1000 K, which may facilitates its applications in a wide temperature range. (C) 2014 Elsevier B.V. All rights reserved.