Effect of In addition on the characteristics of Al–5 wt.%Zn

Samples of Al–5 wt.%Zn and Al–5 wt.%Zn–0.25 wt.%In were prepared then homogenized and drawn in a drawplate into wire of diameter 0.7 mm. The samples were solution treated at 773 K for 2 h then quenched in water kept at room temperature. Immediately after quenching, the samples were crept at different deformation temperatures. Creep curves were obtained under constant stress of 27 MPa and at 383 K, and showed irregular shift. Above 383 K marked increased strain was observed. Both the transient creep parameters, β, n   and εst⋅ increased with increasing temperature. The strain levels were higher for the ternary alloy than those for the binary alloy. The high value of the steady state strain rate exponent γ(=δln⁡β/δln⁡εst⋅), 0.77, was explained in view of the so-called, substeady state creep. The structure variations were traced through the analysis of the obtained X-ray diffraction patterns and SEM micrographs. Although the grain size of the ternary alloy was very small, its high thermal softening led to grain size higher than that for the binary alloy at 423 K.

► Tested alloys irregular shift was observed for creep curves at 383 K.
► Above 383 K the creep parameters β, n   and εst⋅ showed marked increase.
► Addition of In increased the strain levels over the binary alloy.
► The high value of the ratio γ is due to the susbsteady creep state.