High-temperature creep of the intermetallic alloy Ni3Al

Constant stress creep tests have been conducted on Ni₃Al (Hf, B) single crystals in an attempt to characterize the high-temperature creep behavior of this alloy. In contrast to intermediate temperature creep behavior, steady-state creep was observed at 1273 K. This extended steady-state region was formed in less than 1 pct creep strain and lasted for the duration of the creep tests. Primary creep was, however, observed to be limited in nature and consistent with inversetype creep behavior. These observations, preliminary transmission electron microscopy (TEM) observations, and the measured values for the stress exponent(n = 4.3 ± 0.1) and activation energy (Q _c = 398 ± 41 kJ/mole) all suggest that high-temperature creep involves both dislocation mobility and the recovery of dislocation substructure. Attempts to identify a single dislocation mechanism for high-temperature creep were unsuccessful, and it was concluded that a number of slip systems were active at the high temperatures used in these experiments. Formerly Graduate Student, Department of Materials Science and Engineering, Stanford University