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]-ori ented NiAl-1Hf (D209) single crystals has been undertaken. Neither post hom ogenization cooling treatment, minor chemical variations within an ingot or from ingot-to-ingot, nor testing procedure had a significant effect on mec hanical behavior; however a heat treatment which dissolved the initial G-ph ase precipitates and promoted formation of Heusler particles led to a stren gth reduction. Little primary creep was found utilizing direct measurement of strain, and a misorientation of 18 degrees from the [001] did not reduce the creep strength. The effects of heat treatments on properties and a com parison of the how 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 mechan isms. (C) 1999 Elsevier Science S.A. All rights reserved.