Effect of γ' and γ (Ag2Al) precipitates on the steady state creep of Al-16wt%Ag alloys with and without Zr addition

The steady state creep behaviour of Al-16 wt% Ag and Al-16 wt% Ag-0.1 wt% Zr alloys has been studied at constant load (= 137.2 MPa) and tested at different working temperatures for samples aged at temperatures favouring the formation of γ' and γ precipitates. It was found that addition of Zr to Al-16 wt% Ag alloy accelerates the precipitations γ' and γ due to the formation of the metastable phase Al3Zr. For both alloys, two values of activation energy have been obtained as (34 ± 0.3) kJ/mol for viscous glide of dislocations due to the existence of γ' precipitates and (68 ± 0.3) kJ/mol for grain boundary diffusion due to the existence of γ precipitates. TEM investigations of γ' and γ precipitates confirmed the above-mentioned effect of Zr addition. (orig.)