The Localization of Strain in Low Solvus High Refractory (LSHR) Nickel Superalloy

Abstract

The low solvus high refractory (LSHR) nickel base superalloy was chosen as a candidate for a dual microstructure heat treatment (DMHT) turbine disk, with fine grains in the bore and coarser grains in the rim. In between those two regions, there is a transition in grain size and γ′ precipitation. In this study, the mechanical performance of the coarse grain region was evaluated by room temperature tensile testing in the un-aged and dual aged conditions. Optical digital image correlation (DIC) was used to detect the localized strains evolving from the tensile testing. Strain maps from the DIC successfully detected localized strains in both of the microstructural conditions of interest. Transmission and scanning electron microscopy was use to analyze the deformed regions to assess grain misorientation and dislocation activity within each microstructure. While dislocations appeared to accumulate in the gamma channels in both microstructures, there appeared to more grain misorientation in the unaged condition of LSHR.