THE INFLUENCE OF THE DIRECT QUENCH AND INDIRECT QUENCH TO TA-GREATER-THAN-TH ON THE DECOMPOSITION BEHAVIOR OF AN AL-2 AT-PERCENT-ZN-1 AT-PERCENT-MG ALLOY

The decomposition behaviour of an Al‐2.0 at.% Zn‐1.0 at.% Mg alloy after direct quench (DQ) and indirect quench (IQ:T a1 = 23 °C, t a1) to the ageing temperature T a2 = 160 °C (above the temperature of the rapid homogeneous nucleation, Th) was investigated by means of TEM and isothermal resistivity measurements. The precipitation density of the η‐particles yields a maximum value at pre‐ageing times about 10 min at T a1 = 23 °C. To clear up the reason for that phenomenon a loop‐formation and clustering model was introduced. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA