Effect of solution treatment on precipitation and age-hardening response of an Al-4Mg-1Cu-0.5Si-0.4Ag (wt%) alloy

An increase in solution temperature from 520 °C to 560 °C doubled Si concentration (from 0.06 at% to 0.13 at%) in the solid solution of an Al-4Mg-1Cu-0.5Si-0.4Ag (wt%) alloy. Consequently, the alloy exhibited an enhanced age-hardening response with a peak hardness of 135 HVN, 10% higher than that of the alloy treated at 520 °C. The treatment at 560 °C enabled the formation of more Guinier-Preston-Bagaryasky (GPB) zones rather than the Z-phase during subsequent ageing at 200 °C, and hence produced an enhanced strengthening effect to the alloy.