Cryst. Res. Technol.
352000 1 95-100Creep tests under the effect of cyclic stress reduction were conducted to Al-16 wt %Ag and Al-16 wt %Ag-0.1 wt %Zr alloys aged at 548 and 673 K. The steady state creep rate was found to be higher under cyclic stress reduction condition than that under static creep condition for the same maximum stress. An expression for the temperature dependence of the threshold stress for cyclic creep acceleration is offered. Cyclic creep acceleration is interpreted using the dislocation cross-slip model. TEM investigations confirmed that the addition of Zr to Al-Ag alloy accelerates the formation and coarsening of γ \ and γ-phases. The mean value of activation energy for both alloys aged at 548 K was found to be 35±0.3 kJ/mol, and 58±0.4 kJ/mol for alloys aged at 673 K.
The transient creep of Al‐16 wt% Ag and Al‐16 wt% Ag‐0.1 wt% Zr solid solution alloys is investigated in the temperature range 428 to 673 K for various ageing times under constant load. The subsequent decrease and increase in the values of creep parameters n and β with increasing ageing times and ageing temperatures has been explained on the basis of structure transformations occuring in Al‐Ag alloys. It was found that the addition of Zr to Al‐16 wt% Ag alloy accelerates the precipitation of GP zones, γ′‐phase, and γ‐phase. TEM investigations confirmed the above effects. The mean values of the activation energy of both alloys were found to be equal to that quoted for dislocation intersection.
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