Precision control of oxygen content in CP-Ti for ultra-high strength through titanium oxide decomposition: An in-situ study

Oxygen has been known as an effective strengthening element in titanium (Ti) and its alloys. However, an over-dose of oxygen can also lead to embrittlement of Ti alloys. To precisely control and push the limit of oxygen in Ti and its alloys, we studied the decomposition process of Ti oxides in pure α-Ti matrix using an in-situ high-temperature scanning electron microscope. The experimental results revealed that TiO particles decomposed in α-Ti at elevated temperatures and the oxygen atoms gradually diffused into the matrix, following the Fick's second law. Then, the samples with different oxygen contents were produced using the aforementioned strategy, for which the oxygen content, microstructure, and mechanical properties were measured. The results revealed that the oxygen content can be precisely controlled, which can achieve an ultra-high tensile strength of close to 1100 MPa, at no expense of elongation-to-failure, with incorporating 0.87 wt% oxygen. An analysis showed that the strength contribution from oxygen follows the Labusch law. These findings offer a novel approach to design high-performance Ti alloys with non-toxic and cheap elements.