ATOM-PROBE INVESTIGATION OF THE EARLY STAGES OF DECOMPOSITION IN A NICKEL-BASE SUPERALLOY

A conventional time of flight atom-probe has been used for the investigation of the early stages of precipitation of γ' phase in a nickel base superalloy. The microstructure parameters, as derived from concentration profiles, have been studied as a function of the aging time at 650°C. For aging times smaller than a few hours, the precipitate composition varies in a large extent while the particle size remains nearly constant. In contrast, in the coarsening stage γ' precipitates reach their equilibrium composition after the first 25 hours