Slip Localization Intensification Mediated by Grain Boundary Sliding in a Polycrystalline Nickel‐Based Superalloy

This study investigates the effect of temperature on fatigue performance in two polycrystalline Ni‐based superalloys, an Inconel 718 and a René 88DT, with a focus on the plastic localization mechanisms governing crack initiation in the very high cycle fatigue (VHCF) regime. High‐resolution digital image correlation (HR‐DIC) was used to quantify plastic deformation localization and correlate it with fatigue performance across a range of temperatures. While the René 88DT exhibits an increase in fatigue performance with temperature up to , Inconel 718 shows a marked decrease in fatigue performance at . This decrease is attributed to the intensification of slip localization, which is mediated by incipient grain boundary sliding (GBS). These findings reveal an unexpected interplay between slip activity and GBS. This interaction leads to a reduction in fatigue performance of more than twofold.