Effect of Phase Transformation on Creep Characteristics of Zn–0.8 wt% Cu Alloy

Abstract

The creep characteristics of Zn–0.8 wt% Cu alloy have been investigated under different constant applied stresses ranging from 49.52 to 63.67 MPa and at different temperatures ranging from 423 to 493 K. Results of both transient and steady state creep indicated a transition point at 453 K. The transient creep parameters β and n were calculated and found to change with the applied stresses from 10 × 10—4 to 385 × 10—4 and from 0.75 to 0.99, respectively. The strain rate sensitivity parameter (m) was found to change from 0.185 to 0.29 which characterizes a dislocation motion. The activation energy of the transient creep amounted to 66.88 kJ/mol in the vicinity of the transformation temperature (Ttr = 453 K) that is due to dislocation cross-slip along grain boundaries. The activation energies of the steady state creep in the temperature ranges 423 to 453 K and 463 to 493 K were found to be 91.96 and 66.88 kJ/mol as characteristic of the diffusion of Cu precipitates in the Zn-rich phase (η-phase) and dislocation climb, respectively. X-ray analysis confirmed that the above-mentioned mechanisms took place during the creep process.