Relating Microstructure to Defect Behavior in AA6061 Using a Combined Computational and Multiscale Electron Microscopy Approach
21 Pages Posted: 28 Mar 2019 First Look: Accepted
In this study, a multiscale electron microscopy-based approach is applied to understanding how different aspects of the microstructure in a notched AA 6061, including grain boundaries, triple junctions, and intermetallic particles, promote localized dislocation accumulation as a function of applied tensile strain and depth from the sample surface. Experimental measurements and crystal plasticity simulations of dislocation distributions as a function of distance from specified microstructural features both showed preferential dislocation accumulation near intermetallic particles relative to grain boundaries and triple junctions. High resolution electron backscatter diffraction and site-specific transmission electron microscopy characterization showed that high levels of dislocation accumulation near intermetallic particles led to the development of an ultrafine sub-grain microstructure, indicative of a much higher level of local plasticity than predicted from the coarser measurements and simulations. In addition, high resolution measurements in front of a crack tip suggested a compounding influence of intermetallic particles and grain boundaries in dictating crack propagation pathways.
Keywords: Electron microscopy, finite element, ductile fracture, aluminum
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