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

Samples prepared from highly pure Al and Zn were homogenized for 50 h then swaged into wire of diameter 0.7 mm. The samples were solution treated at 773 K for 2 h then quenched in water to room temperature, and immediately, the specimens were aged for 2 h at different temperatures. Creep tests were carried out under constant stress of 27 MPa, constant shear strain amplitude of 5.16 × 10−4 and low frequencies from 0.0 to 3.9 Hz 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, ε ˙ s 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 ( = δ ln β / δ ln ε ˙ s ) , 0.77, was explained in view of the so-called, substeady state creep.