Early stages of decomposition within the γ′ phase of a Ni–Al–Ti model alloy

A Ni-8.5Al-5.4Ti (at.%) model alloy was subjected to a two-step heat treatment resulting in the formation of γ′ precipitates in a γ matrix. The microstructural evolution was followed by transmission electron microscopy. Atom probe analyses at the nanometre scale showed the inhomogeneous distribution of Ni, Al and Ti in the γ′ precipitates. Ni-rich and Ni-depleted clusters were observed. The results are discussed with respect to the excess of Ni within the γ′ phase based on the conditions of heat treatment.