Microstructure based and temperature dependent model of flow behavior of a polycrystalline nickel based superalloy

A physics-driven and microstructure-based model has been formulated for monotonic stress–strain behavior and applied to a polycrystalline nickel based superalloy, René 104. While the yield strength of this alloy is strongly dependent on size and distribution of the ordered γ׳ precipitate, the post-yield behavior is found to be fairly insensitive to the same. Additionally, post-yield hardening and softening rates are found to vary quite significantly within the narrow range of test temperatures examined. For a model to be able to consistently explain all these observations (a) it must explicitly account for microstructural effects and temperature dependence, and (b) it must be aware of the specific strengthening mechanisms unique to nickel-based superalloys. Accordingly, the present effort starts with Estrin׳s dislocation based framework (Estrin (1996) [4]), and then extends the same to incorporate post yield strengthening/softening mechanisms. This paper presents details of this mechanism guided semi-empirical monotonic stress–strain model and its ability to describe flow behavior for different microstructures over a range of temperatures.