Micromechanics of Polycrystalline TI-5AL-2.5SN Using Differential Aperture X-ray Microscopy and Crystal Plasticity Simulation

Understanding the deformation process of crystalline materials at the microscale, also known as micromechanics, is crucial for improving the reliability of structural materials. Therefore, it is essential to find a robust and reliable methodology that can be used to facilitate the study of micromechanics.To this end, near surface plastic deformation processes of a Ti-5Al-2.5Sn sample deformed under uniaxial tension at ambient temperature were analyzed using differential aperture X-ray microscopy (DAXM) and computational models based on crystal plasticity theory. A series of crystal plasticity simulations were conducted in this study using 3D microstructures reconstructed from DAXM data, the results of which indicate that accurate 3D grain morphologies are more important than fine tuning the boundary conditions and the constitutive model when it comes to improving the accuracy of the simulated local kinematic responses (crystal orientation evolution). Furthermore, the effect of 3D grain morphology on the simulated local stress-strain responses was evaluated by comparing them with residual lattice strain/stress tensors extracted from DAXM data, the results of which suggest that the accuracy of simulated local stress state scales with the fidelity of the surrounding reconstructed microstructures. The customized computational toolkits used to extract deviatoric residual lattice strain/stress tensors from DAXM data was also assessed with numerical studies, validating the robustness and the reliability of the customized computational toolkits. Besides reconstructing 3D microstructure and validating simulation results, this work also explores the potentials of extracting dislocation content from DAXM data, which yields a new technique, a Frank-Bilby equation based streak analysis, that is capable of providing misfit dislocation density profile with high spatial resolution.Overall, the work presented in this study demonstrates the potentials of the methodology that combines crystal plasticity simulations with synchrotron radiation techniques for the study of micromechanics. Future development of this methodology should focus on physics-based constitutive model development assisted/validated by the DAXM characterization, which can be of great help for the field of micromechanics.