Microstructure Evolution and Strain Features of a Single Crystal Nickel Base Superalloy during Tensile/Compression Creep
By means of tensile and compression creep testing and SEM, TEM observation, an investigation has been made into the microstructure evolution of a single crystal nickel base superalloy during tensile / compression creep. Results show that the cubic γ′ phase in the superalloy is transformed into the N-type meshlike structure along the direction vertical to stress axis during tensile creep. The cubic γ′ phase is transformed into the P-type structure along the direction parallel to stress axis during compression creep. An obvious asymmetry strain of the alloy occurs during tensile and compression creep, the formation of the needle-like γ′ rafts during compression creep is a main reason of the alloy displaying a smaller strain. During compressive creep, the deformation feature of the alloy is the <110> and (1/3) <112> super dislocations shearing into the γ′ rafts. The deformation mechanism of the alloy, in the stage state of tensile creep, is dislocation climb over the γ′ rafts.
Yafang Han et al.
F. L. Meng et al., "Microstructure Evolution and Strain Features of a Single Crystal Nickel Base Superalloy during Tensile/Compression Creep", Materials Science Forum, Vols. 546-549, pp. 1225-1228, 2007