Deformation Mechanisms in a Co–Ni–Cr Base Superalloy Containing Nb and Al

Abstract

The deformation behaviour of a Co–Ni–Cr superalloy containing Nb and Al has been studied. On aging this alloy is precipitation hardened by cubic shaped γ′ precipitates that precipitate coherently in (100) planes of the FCC matrix. In the underpeakaged condition, the deformation of the alloy causes a shearing of the γ′ precipitate particles by pairs of glide dislocations. In the overaged condition, deformation occurs by the dislocation by-passing mechanism. During the particle shearing stage, the yield strength of the alloy can be satisfactorily explained by the order hardening mechanism due to Brown and Ham. In the overaged condition the Orowan mechanism, as modified by Hirsch and Humphreys, was observed to be applicable.