Effect of oxygen content on the sub-grain nanoindentation response in titanium affected by high temperature oxidation

International audience; Pre-oxidation tests were performed on a commercially pure titanium (CP-40) at 700 °C for 100 h under air in order to introduce a gradient of oxygen content within the metal, also called the oxygen-rich layer (ORL). The chemical profile of oxygen was measured using microprobe analyses (EPMA) on cross-sectional observations. Large but highly resolved nanoindentation maps using continuous stiffness measurement techniques were performed on the specimen cross-section to document the local mechanical response within the oxygen-rich layer (ORL) as a function of the oxygen content and the grain orientation using statistical and multi-modal analyses. The oxygen was found to greatly increase the hardness and elastic modulus in titanium and was correlated to orientation of the c axis of the α-Ti.