Published online by Cambridge University Press: 06 March 2019
Magnesium has been shown to have a marked effect upon preprecipitation processes occurring in aluminum-13 wt.% zinc alloys containing 0.025, 0.098, 0.17, 0.19, 0.23, and 0.27 wt.% magnesium. X-ray small-angle scattering and resistance measurements have been used to monitor the rate of growth of Guinier-Preston zones in quenched foils and wires. The following results have been obtained: (a) small additions of magnesium noticeably decrease the rate of growth of G-P zones but the final zone size reached in the magnesium containing alloys is generally larger than in Al-Zn alloys quenched and aged under identical conditions; (b) the general pattern of preprecipitation found in Al-Zn alloys is not seriously changed by these small additions of magnesium; (c) the dependence of the rate of preprecipitation on quenching temperature is shown to be a function of magnesium content and aging temperature; (d) the dependence of the rate of preprecipitation on aging temperature is influenced by the range of aging temperature, magnesium content, and the quenching temperature.