Frequency and temperature dependence on the creep characteristics of Al-5wt.% Zn alloy

Abstract

Samples prepared from highly pure Al and Zn were homogenized for 50h then swaged into wire of diameter 0.7mm. The samples were solution treated at 773K for 2h then quenched in water to room temperature, and immediately, the specimens were aged for 2h at different temperatures. Creep tests were carried out under constant stress of 27MPa, constant shear strain amplitude of 5.16×10-4 and low frequencies from 0.0 to 3.9Hz superimposed on the static stress during creep test. Both the transient parameters β and n increased with increasing temperature. Increasing frequency decreased β and increased n due to a certain degree of fatigue hardening. The observed decrease of β and steady stat rate, ε̇s after the peak values may be attributed to the coarsening of Al-rich phase particles, which reduces their inhibiting effect on grain boundary. The higher values of β obtained at higher temperatures, were attributed to the reduced crack initiation life associating the existing large grain size. The high average value of γ(=δlnβ/δlnε̇s), 0.77, was explained in view of the so-called, substeady state creep. © 2012 Elsevier B.V..