A phenomenological understanding of the influence of processing methods on creep of Cu-8Cr-4Nb (GRCop-84)

Publication date: Available online 21 April 2019Source: Materials Science and Engineering: AAuthor(s): L.G. Vettraino, M. Zhang, J.L.W. Carter, J.R. Groza, J.C. GibelingAbstractSteady-state creep behavior of rolled Cu-8Cr-4Nb (GRCop-84) production sheet was systematically studied at temperatures from 673 to 1073 K (0.50–0.79 Tm). Threshold behavior was observed at high temperatures and low stresses which can be phenomenologically described by a threshold stress model. The threshold stress obtained by a non-linear regression method ranges from 0.2∼0.3 of the Orowan stress, which suggests that dislocations locally climb over particles with an activation energy approximately equal to that of lattice diffusion. Power-law breakdown was observed at low temperatures and high stresses, which can be phenomenologically described by a hyperbolic sine model. A unifying model is proposed to predict the creep properties of both the production sheet and previously-studied extruded material. Generally, GRCop-84 production sheet creeps faster than the extruded form due to the difference in crystallographic texture. No observable effects caused by microstructural differences are noted to influence the steady-state creep behavior of the two differently processed forms of GRCop-84. The post-fracture morphology of the production sheet closely resembles that of the extruded material indicating ductile fracture caused by micro-void coalescence.
Source: Materials Science and Engineering: A - Category: Materials Science Source Type: research