The influence of Cr and B additions on the mechanical properties and oxidation behaviour of L21-ordered Fe-Al-Ti-based alloys at high temperatures

Several Fe25AlTiX (X = Cr, B) L21-ordered (Heusler phase) alloys with 15 or 20 at.% Ti and varying Cr and B contents have been investigated with respect to their mechanical properties and their oxidation behaviour at elevated temperatures. The mechanical properties have been characterized by means of high-temperature compression tests, four-point-bending tests and creep tests at 750, 800 and 850 °C. The oxidation behaviour has been examined using thermogravimetric analysis at 800 °C in synthetic air. The results show that when Cr and B are added, the latter results in the formation of TiB2, is beneficial for the creep resistance and has no influence on the still-excellent oxidation resistance. However, the alloys show rather high brittle-to-ductile transition temperatures, which can be lowered by the addition of TiB2 as a result of grain refinement.