Structural and Oxidation Studies of Titanium Beryllides

The improved mechanical and chemical properties of intermetallic beryllium compounds make them good candidates to replace metallic beryllium in future fusion power plants. Titanium beryllide is a compound with low chemical reactivity, which makes it very attractive for fusion applications. In this work we study the structural stability of titanium beryllides and the oxidation behavior under air annealing. Both high-resolution X-ray diffraction and microbeam techniques were used to follow the evolution of the composition and crystalline phases as well as the microstructure. Beryllium-titanium intermetallic compounds were produced using two alloys with a nominal composition of Be-5 at.% Ti and Be-7 at.% Ti. The as-cast samples show the presence of Be₁₀Ti for the Be-7 at.% Ti alloy, while the Be₁₂Ti phase was mostly found in the Be-5 at.% Ti compound. While the Be-5 at.% Ti alloy reveals large intragrain regions with high concentration of impurities (O, Fe) and Ti depletion, the Be-7 at.% Ti shows a more homogeneous structure. During thermal treatments up to 800°C in dry-air atmosphere, the oxidation occurs preferentially at the beryllium-rich regions. No evidence was found for phase separation during the annealing in vacuum.