In-situ high energy X-ray diffraction study of the elastic response of a metastable β-titanium alloy

In the present work, the elastic behavior of a metastable β-Ti alloy, Timetal-18, is studied in the β-quenched condition using in-situ far-field (ff) and near-field (nf) high energy synchrotron X-ray diffraction microscopy (HEDM) techniques and full-field crystal elasticity simulation. HEDM enables assessment of the 3D microstructure as well as the complete (6 components) elastic strain tensor and crystallographic orientation of each grain in the gauge volume of a polycrystalline aggregate. Using this elastic strain and orientation data from ~100 grains, a straightforward strategy to obtain the single crystal elastic constants (SEC) is demonstrated. The elastic moduli thus obtained are (in GPa): C₁₁ = 118 ± 5, C₁₂ = 79 ± 3, C₄₄ = 39 ± 4, with a Zener anisotropy ratio (A) of 2.0 ± 0.4. The nf-HEDM 3D microstructure was used to instantiate a virtual microstructure, as input into the parallelized code, Micromechanical Analysis of Stress-strain Inhomogeneities with fast Fourier transform (MASSIF), in order to simulate the grain level constitutive response. The predicted evolutions of the elastic strain tensor components are shown to be in good agreement with the measured values. However, grain-by-grain comparisons emphasize the strong effect of elastic anisotropy, suggesting it may be even higher than A = 2. The accuracy of the approach and implications for modeling the grain-level constitutive response in the plastic regime are discussed.