The influence of small Mg additions on the stability of guinier-preston zones in Al4.5 at% ZnxMg alloys

Abstract

The influence of small Mg additions (xMg ≦ 0.20 at%) on the upper Limit temperature T GPZdiss of the existence of Guinier‐Preston (GP) zones is determined by SAXS investigations. In order to avoid falsifications by the size dependence of T GPZdiss, in all cases, the reversion treatments start with GP zones having a mean size of RK = (2.1 ± 0.2) nm. The main results are: (i) up to xMg = 0.10 at% T GPZdiss = (118 ± 3)°C, i.e. only few Mg atoms are inserted into the GP zones, but if adding 0.20 at% Mg to the Al4.5 at% Zn mother alloy T GPZdiss is raised to (152 ± 3)°C; (ii) the solubility of Mg in the matrix of the Al4.5 at% Zn mother alloy is less than 0.20 at%.