Dislocation/precipitate interactions in IN100 at 650 °C

The influence of γ′ size on critical resolved shear stress in alloy IN100 at 650 °C has been examined by considering dislocation/precipitate interactions involving particle shearing and Orowan by-passing mechanisms. To achieve this, heat treatment procedures were carried out on smooth specimens to produce materials with variations in secondary and tertiary γ′ size, while maintaining their respective volume fractions. These specimens were subjected to strain-controlled fully reversed cyclic loading at 650 °C. Thin foils extracted from these specimens, post-testing, were examined by transmission electron microscopy to identify the nature of the precipitate/dislocation interactions during plastic deformation. Results indicated the presence of shearing and Orowan by-passing mechanisms. These observations have been used as a basis to calculate the critical resolved shear stress as a sum of components contributed by solid solution and by γ′ particles being sheared and looped. In this analysis, a critical particle size defining the shearing/looping transition has been determined and this has been used to calculate the relative volume fraction and size of particles contributing to the critical resolved shear stress. These analytical results have been compared with those experimentally obtained at 650 °C using smooth specimens with different precipitate sizes.