RuAl and its alloys, Part II: Mechanical properties, environmental resistance and applications

Part II of the review (Part I: Intermetallics 2005;13:5) presents the latest research status on mechanical properties, environmental resistance and applications. Mechanical properties of single crystals and polycrystalline material are presented as a function of orientation, temperature, composition, and alloying elements. Due to microstructural effects, distinction between single-phase, near single-phase, and multiphase polycrystalline alloys is essential. In addition, fracture behavior is discussed. Environmental resistance of RuAl alloys takes into account oxidation, corrosion and plasma erosion resistance, with emphasis on high-temperature oxidation and plasma erosion.Concluding this overview, single-phase RuAl simultaneously shows good oxidation resistance, exceptional thermodynamic stability and high strength at high temperatures, as well as great ductility at room temperature. Moreover, the thermal expansion coefficient of RuAl is nearly equal to that of α-Al2O3 which is required for good oxide scale adherence. This outstanding combination defines the role of RuAl among comparable intermetallics during prospective improvement of high-temperature applications.