Ductile Silicide Alloys

The demand for improvement in the perf ormance and ef f iciency of modern turbines requires the development of advanced materials which retain high strength, creep and oxidation resistance at increasingly elevated temperatures. Many materials meet the high-temperature criteria, for example ceramics, some intermetallic compounds and metallo-ceramics such as MoSi2, but suffer from a lack of toughness, either because of persistent brittleness at high temperatures or because a ductile-brittle transition (DBT) takes place between operating and room temperatures. Critical to the utility of these materials is an understanding of the mechanisms responsible for the DBT and specific indication of how the impact of the DBT can be minimized or avoided. This proposal will focus directly on MOS'21 an MC material which, at high temperatures, combines the strength typical of ceramics with the toughness of metals. The proposed work will use an innovative, inter-disciplinary technique (combining fundamental quantum mechanics with materials science) to evaluate the temperature dependence of dislocation nucleation and mobility and hence determine the origin of the DBT in MOS'2. From this a prescription will be developed for increasing the fracture toughness of MOS'2 by microalloying to eliminate or control the DBT.