Deformation mechanism for high temperature creep of a directionally solidified nickel-base superalloy

The steady-state creep behavior of a DS nickel-base superalloy (DZ17G) have been investigated in terms of a Dorn creep law. Both the apparent stress exponents measured and TEM observations indicate that the creep mechanism changes from the dislocation climb around γ′ precipitates at low applied stress to the dislocation cutting through γ′ precipitates at high applied stress. This transition can be interpreted by a modified Dorn creep law involving a threshold stress term. The theoretical values of the threshold stresses calculated in terms of Brown-Ham and Labusch-Schwarz models are in close agreement with the experimental results.