Abstract
The aging and split aging characteristics of ternary aluminium-zinc-magnesium alloy with zinc contents of 3, 4.5, 6 and 7%, and magnesium contents of 1, 2 and 3% were investigated. Aging curves are determined as a function of tensile properties at the room temperature, 90°, 120° and 150°C.
In determination of split aging characteristics, the first stage aging was done in the room temperature with practical point of view and the second stage aging at 90°, 120° and 150°C was followed.
Conclusion are as follows:
1) In ternary Al-Zn-Mg alloys, increasing Zn amount accelereted the rate of age hardening and increase of Mg increases the strength of matrix. The strength of alloys increase with the amount of (Zn+Mg), but Mg has stronger effect than Zn.
2) Tensile strength of Al-Zn-Mg alloys aged at 120°C, do not differ from that of the alloys aged at 90°C, but yield strength showed maximun value at 120°C. In the range of low Zn+Mg%, the difference of aging temperature of 90° and 120°C has little influence on the value of tensile and yield strength, but tensile properties are generally low at the aging temperature of 150°C.
3) The Al-Zn-Mg alloy has remarkable split aging effect and from the practical point of view, the room temperature aging is necessary before the artificial aging. This split aging effect relates closely to the composition and the second stage aging temperature.
4) The influence of Mn and Cr on aging and split aging characteristics are almost negrigible.
