Micromechanisms of High-Temperature Fatigue-Crack Growth and Low-Temperature Toughness in Monolithic and Composite Intermetallic Alloys.

摘要

The next generation of high-performance gas-turbine engines will require stiffer materials, operating at higher stress levels and capable of withstanding higher temperatures. Candidate materials for such applications include ordered intermetallics, ceramics and composites based on metal, intermetallic, ceramic and carbon matrices, all of which are currently of limited use due to their low ductility and toughness at room temperature. Several toughening strategies have been explored to develop intermetallic alloys for structural use, and their room temperature crack-growth properties, both under monotonic and cyclic loading, have been recently characterized in some detail. However, there is still a paucity of crack-growth data in these materials, especially at high temperatures, and a lack of understanding of the salient mechanisms governing crack growth in these materials at these temperatures. Accordingly, the present research is aimed at examining the fatigue-crack growth and fracture behavior in various intermetallic alloys, with special emphasis on the effect of ambient-temperature toughening mechanisms on high-temperature cyclic crack-growth resistance.