Novel fully-lamellar Mo + Mo5Si3 eutectoid alloys by macro-alloying with TiWednesday (28.09.2016) 17:30 - 17:45 Part of:
Structural engineering materials with high strength and oxidation resistance at elevated temperatures are highly desirable for applications which potentially increase efficiency in aircraft engines and power generation. Due to their high melting points, both Nb- and Mo-silicides fulfill several of these requirements: while Mo-Si-B alloys show better creep and oxidation resistance at high temperatures, Nb-silicides are in general more ductile at room temperature and possess lower density. However, it was found recently that macro-alloying with Ti can replace the Mo3Si phase with more oxidation resistant Mo5Si3 in Mo-Si-B alloys. Additionally, the creep strength increases compared to Ti-free Mo-Si-B and the density decreases significantly. Another peculiar feature in Mo-Si-B-Ti alloys is the eutectoid reaction of Mo3Si to Mo + Mo5Si3.
This talk will highlight the option to generate a fully-lamellar Mo + Mo5Si3 microstructure by macro-alloying with Ti. Those alloys were produced via repetitive arc-melting of high-purity metals and Si in a Zr gettered high-purity Ar atmosphere. Subsequent, heat treatments at temperatures ranging from 1200 to 1400°C are applied in order to promote the eutectoid decomposition. Microstructural analyses were carried out by SEM and EBSD, while ensuing mechanical properties were investigated by compression creep tests at temperatures up to 1200°C.