Constant-stress creep tests were 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 1273K. This extended steady-state region was formed within less than 1% creep strain and lasted for the duration of the creep tests. Primary creep was, however, observed to be limited in nature and consistent with inverse type creep behavior. These observations, preliminary transmission electron microscopy observations, and the measured values for the stress exponent (n = 4.3) and activation energy (398kJ/mol) all suggested that high-temperature creep involved both dislocation mobility and the recovery of dislocation sub-structures. 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.

High-Temperature Creep of the Intermetallic Alloy Ni3Al. Hemker, K.J., Nix, W.D.: Metallurgical Transactions A, 1993, 24[2], 335-41