Mechanochemical synthesis and compaction of nanocomposites based on Ni3Al intermetallic compound containing carbon and carbide-forming elements

Ni(Al, C) mixed (substitutional and interstitial) solid solutions have been synthesized by mechanical alloying; the atomic ratio of Ni and Al was constant at 3: 1, but the concentration of carbon was varied. A carbide-forming element CE (Ti, Nb, or Hf) was added to the formed solid solutions with nanocrystalline substructures; the size D of coherent scattering regions was 4–6 nm. These mixtures Ni(Al, C) + CE were subjected to mechanical activation (short-term milling) and subsequent hot isostatic pressing. According to X-ray phase analysis, compacted samples exhibited three phases: Ni3AlC x antiperovskit, Ni(Al) solid solution with D = 50–100 nm and corresponding metal monocarbides (TiC, NbC, or HfC; D ≈ 7 nm) located at boundaries. These results were confirmed by scanning electron and optical microscopy. Thus, we obtained the analog of the conventional high-temperature γ/γ′ alloys hardened by grain-boundary nanoscale carbides, which prevent recrystallization.