Abstract:The ageing behavior and microstructures of the Al-4Mg-1.5Cu alloys containing silver and lithium have been studied. The results show that the effect of Li is to increase the rate of hardening, however, lithium additions in the range of 0 to 2.0% does not progressively change age hardening and precipitation process in the alloy of Al-4.0Mg-1.5Cu-0.4Ag-0.12Zr aged at 200℃, and significant age hardening and strengthening response only occur with the addition of 2.0%Li. TEM investigation results show that the remarkable increase of age hardness and strength is attributed to the fine dispersion of δ′, Z phase and spherical Al₃Zr/Al₃Li compound particles in the 2.0%Li-containing alloy.

Key words: Al alloy; ageing; microstructure; lithium; silver