An oxide-dispersion-strengthened Ni3Al-based alloy was produced by mechanically alloying a 76Ni-19Al-5Cr-0.1at%B powder with 2vol%Y2O3, and then consolidating by hot extrusion. A microstructure with large elongated grains and an 11:1 grain aspect ratio was developed by secondary recrystallization heat treatments. The creep rate as a function of stress for this coarse-grained material was evaluated at 649, 732, 816 and 982C. At 649C and stresses of 557 to 695MPa, power law creep with a stress exponent of 13.5 was observed. In the range of 732 to 816C a stress exponent of 5.1 and an activation energy of 239kJ/mol were observed. At stresses above 566MPa at 732C, and above 456MPa at 816C, the observed stress exponents were 22 and 13 respectively. At 982C and stresses of 133 to 311MPa a stress exponent of 9.1 was observed. The high stress, high creep rate behavior resulted from the bulk deformation of grains, whereas the low stress, low creep rate behavior resulted from the constrained growth of cavities on transverse boundaries. For all conditions of temperature and stress (except 311MPa at 982C) this coarse-grained oxide-dispersion-strengthened Ni3Al alloy exhibited creep rates for a given stress which were at least a factor of 10 less than those of other polycrystalline or single-crystal Ni3Al alloys. The observed creep rates were, however, greater than those of the more complex commercially available superalloys.

Creep Behavior of an Oxide-Dispersion-Strengthened Ni3Al-Based Alloy. Mason, R.P., Grant, N.J.: Materials Science and Engineering A, 1995, 192-193[2], 741-7