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 fro m 42 to 50.3 MPa at different temperatures in the range from 503 to 62 3 K. Variations of creep characteristics are studied by subjecting the alloy samples to different degrees of pre-deformation in the same tem perature range under a constant stress of 42.04 M Pa. Pre-deformation increases the total creep strain and clears out the superplastic behav iour of the transient creep as an intensive increase for the parameter s 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 temperatur e of the alpha'-phase. The integrated role of stress, pre-deformation, and temperature is cleared. The observed structural variations and th e calculated activation energies suggest a dislocation mechanism invol ving grain boundary sliding or migration as the rate controlling mecha nism for transient creep in Al-40 wt% Zn alloy.