PHASE CHARACTERISTICS OF PRE-DEFORMED AL-40 WT-PERCENT ZN ALLOY

The total creep strain rate and the transient creep parameters B and n of Al-40 wt% Zn alloy are studied under constant stresses ranging from 42 to 50.3 MPa at different temperatures in the range from 503 to 623 K. Variations of creep characteristics are studied by subjecting the alloy samples to different degrees of pre-deformation in the same temperature range under a constant stress of 42.04 M Pa. Pre-deformation increases the total creep strain and clears out the superplastic behaviour of the transient creep as an intensive increase for the parameters B and n and a decrease for the energies activating the creep process. The observed peaks for B and n are rendered to the softer beta-phase and due to the state of the alloy being near the eutectoid temperature of the alpha'-phase. The integrated role of stress, pre-deformation, and temperature is cleared. The observed structural variations and the calculated activation energies suggest a dislocation mechanism involving grain boundary sliding or migration as the rate controlling mechanism for transient creep in Al-40 wt% Zn alloy.