Tensile and creep behavior of cryomilled Inco 625

The tensile and creep behavior of a cyromilled Inconel 625 alloy have been investigated. The microstructure is duplex with grain sizes ranging from 200 nm at the smallest to about 10 pm at the largest. Normal work hardening is observed in uniaxial tension and the stress-strain behavior follows a power law. Deformation of this material is accomplished by dislocation motion as evidenced by TEM examination of deformed samples. The primary source of strengthening comes from grain size refinement. Additional factors such as solid solution strengthening contribute to a lesser extent. Analysis of the high temperature creep behavior reveals that cryomilled Inconel 625 exhibits characteristics of structure controlled (Class II) as well as mobility controlled (Class I) creep behavior. The true activation energy for creep for both structure controlled and mobility controlled creep exceeds the value for lattice self-diffusion in Ni. This is explained in terms of the simultaneous deformation of second phase particles along with the Ni matrix during high temperature creep deformation. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.