Fatigue-crack growth of small cracks in a directionally-solidified nickel aluminide with molybdenum additions

摘要

In recent years, aluminide intermetallic compounds, such as NiAl and TiAl, have been contemplated for potential high-temperature structural use in aero-engine applications as possible replacement for the nickel-base superalloys. NiAl, for example, has a relatively low density (5.95 g/cm3) approximately two-thirds that of superalloys, extremely high oxidation resistance and high thermal conductivity (1). However, like many intermetallics, its application is severely compromised by its very low ductility and toughness properties at ambient temperatures; moreover, NiAl displays lower strength at elevated temperatures. Accordingly, much alloy design and microstructure research on NiAl has been focused on attempts to improve the low-temperature ductility, fracture toughness and high-temperature strength of this intermetallic (2-7).