High-temperature deformation behavior of NiAl(Ti) solid-solution single crystals

The high-temperature deformation behavior of the solid solution-strengthened alloys Ni-47.5Al-2.5Ti and Ni-47Al-3Ti were investigated. Single crystals were deformed in compression in the “hard” 〈001〉 and “soft” 〈111〉 orientations, at temperatures between 827 °C and 1250 °C. The results show that Ti has a very powerful solute-strengthening effect in NiAl. The creep rates for the solid-solution alloys were observed to be as much as three to four orders of magnitude lower than those for unalloyed NiAl. To better understand this strong solid-solution strengthening effect, we studied the stress and temperature dependence of the creep rates for these alloys, as well as the deformation transients associated with stress changes. These results suggest that solute-drag effects dominate the creep resistance at the highest temperatures and lowest stresses. The solute-drag hypothesis is supported by calculations of the solute-size effect of Ti in NiAl and by the form of dislocation substructures found in the creep-deformed crystals. W.D. NIX is the Lee Otterson Professor of Engineering with the Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305.