Effect of preaging on precipitation behavior in aluminum alloy 6063 during high‐temperature aging

The influence of low-temperature preaging on the artificial age-hardening of a aluminum alloy 6063 (Al-0.72Mg-0.42Si) has been investigated in this study. The precipitation behaviors of samples of the alloy were analyzed using differential scanning calorimetry as well as by measuring the electrical resistivity, and confirmed by microstructure observation using transmission electron microscopy. Tensile tests were performed to determine the mechanical properties of the samples. The results indicate that GP zones (I) are formed in the aluminum alloy 6063 at 0-30°C during a long preaging period. The formation of GP zones (I) will retard the precipitation of the intermediate β' phase during artificial aging and will result in decrease in the strength of the alloy after the artificial aging process. Increasing either the preaging temperature or the holding period will significantly decrease the strength after artificial aging. The results indicate that GP zones (II) are formed in the Al alloy 6063 at a preaging temperature of 40-70°C but this has no influence on age-hardening after artificial aging, even for a long period. Increasing either the preaging temperature or the holding period will significantly increase the strength after artificial aging. However, for preaging at -10°C, the negative effect on age-hardening is still not clear and should be investigated in the future.