Microstructure evolution and element-diffusion mobility of DZ125 nickel-based superalloy during creep

By means of creep-curve measurements and microstructure observations, combined with the calculation of element-diffusion mobility, the microstructure-evolution regularity of DZ125 nickel-based superalloy during creep at 1 040 ℃ was investigated. The results show that, during high-temperature creep, inhomogeneous microstructure evolution occurs in the interdendrite and dendrite arm regions. The coarser rafted γ′ phase appears in the interdendrite regions, the fine rafted γ′ phase with the mesh-like N-type structure on(001) plane forms in the dendrite arm regions, and the γ matrix phase fills continuously between the mesh-like rafted γ′ phase to ensure the better plasticity of the alloy. During creep at(1 040 ℃, 137 MPa), the cuboidal γ′ phase in the dendrite arm region transforms into the rafted structure after being crept for 3 h. As the applied stress decreases, the rafted time of γ′ phase prolongs. Thereinto, the bigger diffusion mobilities of elements Al and Ta are the main reason for the alloy occurring rapidly microstructure evolution.