Characteristics of thermal transitions during annealing of a nanocrystalline Ni3Al-based alloy

In this study, the changes in atomic ordering of a Ni3Al-based alloy were investigated. The mechanically alloyed powders were annealed at different temperatures up to 1300 °C and then subjected to X-ray diffraction (XRD) analysis. In addition, differential thermal analysis (DTA) with different heating rates was used for calculating the activation energy (using Kissinger and Augis & Bennet methods) and enthalpy of the three transitions: atomic ordering of crystalline structure, transformation of γ′-L12→γ-fcc and melting. According to the results obtained, the maximum atomic ordering in this Ni3Al-based alloy obtained at 600 °C, beyond which it decreased with increasing temperature. Ultimately, atomic ordering completely vanished at 1300 °C due to a lattice transformation occurring from L12 ordered structure to the Ni-based solid solution phase.