1300 K creep behavior of [001] oriented Ni–49Al–1Hf (at.%) single crystals

A study of the 1300 K compressive and tensile creep properties of [001]-oriented NiAl–1Hf (D209) single crystals has been undertaken. Neither post homogenization cooling treatment, minor chemical variations within an ingot or from ingot-to-ingot, nor testing procedure had a significant effect on mechanical behavior; however a heat treatment which dissolved the initial G-phase precipitates and promoted formation of Heusler particles led to a strength reduction. Little primary creep was found utilizing direct measurement of strain, and a misorientation of 18° from the [001] did not reduce the creep strength. The effects of heat treatments on properties and a comparison of the flow stress–strain rate data to those predicted by the Jaswon–Cottrell solid solution hardening model indicate that the 1300 K strength in NiAl–1Hf single crystals is mainly due to precipitation hardening mechanisms.