Creep behaviors and role of dislocation network in a powder metallurgy Ni-based superalloy during medium-temperature

By means of creep propertiesmeasurement, microstructure observation and contrast analysis of dislocation configuration, the creep behaviors and role of dislocation networks in FGH95 powder metallurgy Ni-based superalloy during creep have been investigated. The results show that the microstructure of alloy consists of the fine γ′ phase coherently embedded in the γ matrix, and a few coarser γ′ particles are distributed in the boundary regions. In the ranges of the applied temperatures and stresses, the alloy displays a better creep resistance and longer lifetime. The deformation mechanisms of alloy during creep are the dislocations slipping in the matrix and shearing into the γ′ phase, and the dislocations shearing into the γ′ phase may be decomposed to form the configuration of the partials plus the stacking fault. During creep, two groups of dislocations on different slip planes may knit to form the quadrangular dislocation networks; while two groups of moving dislocations on the same slip plane may encounter and react to form the hexagonal dislocation networks. The strength of boundaries is responsible for the creep resistance of alloy, and the one is related to the deforming behaviors of coarse γ΄ particles distributed in the boundaries. Thereinto, the dislocation networks distributed in the interfaces of coarse γ′/γ phases may release the lattice-misfit stress and relax the stress concentration to delay the dislocation shearing into the γ′ phase, which is beneficial to keep the boundary strength and enhance the creep resistance of the alloy.