High temperature creep of directionally solidified ni base superalloys containing local recrystallization

Abstract

High temperature creep of directionally solidified Ni-base superalloys containing local recrystallization (RX) was studied. An almost linear reduction of the creep rupture life was observed with increase of the fraction of local RX on the cross section of the specimen. Creep curves of specimens containing local RX showed that the second and tertiary creep stages were much shorter than those of the original specimens. Moreover, their creep rates slightly increased before reaching the steady state. The change of creep rate is related to the formation and propagation of cracks at the RX grain boundaries according to the observation of the interrupted creep microstructure. The creep mechanisms were discussed based on the dislocation morphology in the vicinity of the RX grain boundaries.