Effect of precipitation on elastic modulus of Al-Zn-Mg-Cu-Li alloys

Al-5.6Zn-3.0Mg- 1.6Cu- 1.1Li-0.24Cr alloys and Al-8.0Zn-2.4Mg-2.4Cu- 1.1Li-0.18Zr altoys （mass fraction, %） were aged by different processes. The microstructure and mechanical properties were determined by transmission electron microscopy（TEM）, tensile test and Vicker＇s hardness test. The experimental results show that the most signified hardening is obtained by double-ageing or multi-ageing for the Al-Zn-Mg-Cu-Li alloys. The yield strength and the elastic modulus of the Li-containing alloys have relationships with ageing processes. The elastic modulus of Li-containing alloys decreases with the increment of precipitates though it is higher than that of Al-Zn-Mg-Cu alloy.