Effect of Li additions on the age hardening response and precipitate microstructures of Mg–2.4Zn–0.16Zr based alloys

► Enhancement of age hardening response of Mg–2.4Zn–0.2Zr alloy by addition of 2at% Li. ► The time to reach peak hardness has been reduced to 1/3 by adding Li. ► The enhancement of mechanical properties was attributed to the refinement in the microstructure. The effect of Li additions and microalloying with Ag and Ca on the age hardening of a Mg–2.4Zn–0.16Zr alloy is studied. The addition of Li up to 2at% enhances the age hardening response. The major precipitates in the peak aged condition at 160°C are Mg4Zn7 in which Li is preferentially partitioned. Further addition of trace amounts of Ag and Ca enhances the age hardening response. The size, the number density and the morphology of the precipitates are investigated by transmission electron microscopy and three dimensional atom probe to interpret these results.