First experimental evidence of oxygen ordering in dilute titanium-oxygen alloys

Small addition of oxygen is currently used to improve the mechanical properties of titanium. It has been thought, until now, that oxygen fully dissolves in the titanium matrix, thus leading to a solid solution. However, we show here, with transmission electronic microscopy and X-ray diffraction, that oxygen can also form ordered precipitates with a Ti₆O-type structure, even for a concentration a slow as 0.15 wt % O. The ordered precipitates found in a series of pure binary Ti-O alloys are also visible in commercially pure titanium, including grades 2 and 4, two compositions widely used for technological applications. (authors)