Effect of oxygen content on elastic properties of an oxygen-graded titanium: Experimental and computational analyses

High-speed nanoindentation mapping (HSNM), electron backscatter diffraction (EBSD), electron microprobe analyses (EPMA), and high resolution – microscale laser induced breakdown spectroscopy (HR–μLIBS), were used to characterize the evolution of the elastic anisotropy of a commercially pure titanium (CP-Ti) having a gradient of oxygen concentration. CP-Ti samples were pre-oxidized in air at 655 ∘C for 120 h to create a 35 μm-deep gradient of oxygen within Ti, the oxygen-rich layer (ORL). Wedge-cut samples were prepared to spread the ORL over hundreds of micrometers instead of tens of micrometers for cross-sections. EPMA and HR–μLIBS were used to quantify the oxygen distribution within the ORL in a relative and absolute manner, respectively. The Vlassak-Nix theory was used for inverse identification of the stiffness matrix terms as a function of the oxygen content. The stiffness matrix as a function of the oxygen concentration was used to simulate the stress–strain distribution at the sub-grain level in the ORL under tensile macroscopic loading. Configurations with and without external oxide were numerically tested to investigate the role of the oxide layer on the stress distribution within the ORL as well as the crystallographic texture.