Microstructure effects and modelling of Incoloy 800 behaviour

At 550 0C Incoloy 800 undergoes γ' hardening. The phase dispersion characteristics, which closely control the strength properties, are time dependent. The behaviour of Incoloy 800 has been studied with mechanical cycle tests. A microstructural study, from which an analysis of the γ' precipitate size effect on the strain phenomena and on rupture at high temperature could be made, was undertaken. A model is proposed which is able to describe the cycle consolidation phenomenon for low cycle fatigue and the fatigue stress relaxation tests, when using the characteristic parameters of the γ' precipitation. (U.K.)