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Abstract
The localisation of plastic strain in polycrystalline metals is influenced by the microstructure. In this work, we study the localisation and heterogeneity of the plastic response using high resolution strain measurements via digital image correlation and microstructural characterisation using electron backscattering diffraction in monotonic tension, fatigue, and creep. We focus on the role of grain boundaries acting as barriers to dislocation motion. More specifically, we address slip transmission across grain boundaries and the importance of the residual Burgers vector in determining the cross-boundary reaction. We provide insight into how these cross-boundary reactions influence the accumulation of plastic strains across interfaces, dictate the locations of fatigue cracks, and affect the length of fatigue microcracks. The scope of the paper is partially a summary and overview of most recent published work as well as presenting new experimental results, particularly at elevated temperatures. The main outcomes of the agglomerate of experimental and analysis results are discussed with the intent to provide a deep understanding of the plastic response of the nickel-based superalloy, Hastelloy X, at different length scales and different loading and temperature conditions.
Funding
This work was funded by the Midwest Structural Sciences Center (MSSC); Air Vehicles Directorate of the U.S. Air Force Research Laboratory [grant number FA8650-06-2-3620]; EBSD results were obtained at the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the U.S. Department of Energy [grant number DE-FG02-07ER46453], [grant number DE-FG02-07ER46471].