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

The compressive properties of near 〈0 0 1〉 and 〈1 1 1〉-oriented NiAl–2Cr single crystals and near 〈0 1 1〉-oriented NiAl–6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the 〈1 1 1〉 and 〈0 0 1〉 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 〈0 1 1〉-oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 K and 1500 K; whereas both 〈0 0 1〉 and 〈1 1 1〉 NiAl–2Cr 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 〈0 0 1〉-oriented NiAl–2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for 〈0 0 1〉 crystals.