Slow plastic compressive behavior of NiAl-xCr single crystals at 1100-1500K

The compressive properties of near < 001 > and < 000 > -oriented NiAl-2Cr single crystals and near < 011 > -oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the < 111 > and < 001 > single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The < 011 > -oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 K and 1500 K; whereas both < 001 > and < 111 > NiAl-20 crystals possessed stress exponents near three which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of three at 1500 K for < 001 > -oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for < 001 > crystals.