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Abstract: A new Ni3Al-based alloy has been successfully made via densification of mechanically alloyed powders with nominal compositions of Ni–8.14Al–7.83Cr–1.45Mo–0.01B (wt%). Mechanical alloying (MA) was carried out in a planetary ball mill under different conditions. The effect of MA on the structure of elemental powders was investigated. A Ni-based solid solution was produced after 10h of milling that transformed to a disordered Ni3Al intermetallic compound with nanocrystalline structure on further milling. The rate of this transformation depended on milling variables such as mill rotation speed and milling media. The yield strength of produced alloy increased with increasing temperature up to 600°C beyond which it decreased. [Copyright &y& Elsevier]

Abstract: The characteristics of specimens produced from a Ni3Al-based alloy using four different routes were investigated and different trends during consolidation of mechanically alloyed (MA-ed) powders were characterized and analyzed using microstructural observations; measurement of long-range order (LRO) parameter, micro-strain, and grain size; as well as determination of microhardness and density. In addition, the compressive yield strength and ductility of two series of specimens at different temperatures were determined. It was observed that hot pressing (HP) led to the best consolidation conditions. In addition, high pressure cold pressing (CP)/sintering caused the consolidated specimens to improve. In all specimens, the nature of nanocrystalline powders remained unchanged and the disordered MA-ed powders were ordered during consolidation. The yield strength in both series of specimens anomalously increased with increased temperature by up to 600°C, which later decreased beyond this critical temperature. [Copyright &y& Elsevier]

Abstract: 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 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. [Copyright &y& Elsevier]