The high temperature (1083 to 1388K, 0.65 to 0.84Tm) creep behavior of single crystalline Ni3Al(Ta,B) was investigated. A change in the creep characteristics as a function of applied stress was observed at the uppermost testing temperatures of 1288 and 1388K. At low applied stress levels the Norton law stress exponent was equal to 4.3; for higher stresses the stress exponent was equal to 3.2. Different creep curves were observed, depending on the value of the stress exponent. The change in stress exponent and nature of the creep curve correspond to a change in the controlling deformation mechanism from dislocation climb to viscous dislocation glide for Ni3Al(Ta,B). The experimentally observed transition stress values between climb and viscous glide were in good agreement with values predicted from theory, assuming that the major force retarding viscous dislocation glide in Ni3Al(Ta,B) was the antiphase boundary interaction.

High Temperature Creep Transitions in Single Crystalline Ni3Al(Ta,B). Wolfenstine, J., Kim, H.K., Earthman, J.C.: Journal of Materials Research, 1993, 8[10], 2510-4