Martensitic transformation and characterisation of the structure of a NiAl - Ni3Al alloy

A microstructural study of a Ni-32at.%Al-5 at.%Fe intermetallic alloy has been performed by electron microscopy and X-ray diffraction analysis. The martensitic (L10) and the Ni3Al (γ′) phases have been observed in the as-cast alloy. Details of the martensitic transformation are studied by in situ heating and cooling experiments. It has been observed that annealing in the (β + γ′) phase region leads to the reverse martensitic transformation of the L10 phase to the NiAl (β) phase and to NiAl → Ni3Al phase transformation. The volume fraction of the Ni3Al phase increases with increasing annealing temperature.