3d Microscale Characterization and Crystal-plastic Fe Simulation of Fatigue-crack Nucleation and Propagation in an Aluminum Alloy

Critical steps toward designing and developing modern materials include observing, simulating, and predicting 3D deformation and cracking mechanisms at various length scales. In this work, advanced characterization and simulation techniques are employed to study the micromechanisms involved in nucleation and propagation of fatigue cracks in an aluminum alloy used in pressure-vessel structures. In addition to electron-backscatter diffraction and scanning-electron microscopy, post-mortem (ex-situ) X-ray tomography and high-energy Xray diffraction microscopy are used to characterize in 3D the microstructural features, including grain geometries and orientations, local to crack surfaces. Digital reconstructions (viz. 3D crystal-plastic finite-element models) are generated as a way to simulate the observed crack-evolution behavior and thereby compute local response fields along measured crack fronts in 3D. A better understanding of deformation and cracking mechanisms in 3D at the microscale will allow for better predictive modeling, which will be essential to both expedite and expand materials design.