Stress saturation in a nickel-base superalloy, under different aging treatments

The effect of γ′-precipitates on the saturation stress, extrapolated from stage III of work hardening (WH), has been studied in the superalloy Inconel X-750 on two situations, the solution heat treated, and peakaged-overaged samples. The WH was analysed by means of diagrams θ=dσ/dε versus σ, and Θd=dσd/dε versus σd, where σ is the flow stress and σd is the dislocation related stress component of σ, obtained by the application of a superposition rule. The results indicate that, for the overaged alloy, the storage of dislocation loops leads to a high initial WH rate; but during stage III a strong dynamic recovery reduces the effect of the precipitates on the saturation stress. The influence of the superposition rules, used in the data analysis for the interpretation of the saturation stress in terms of the dislocation density, was also discussed.