Enhanced precipitation hardening of Mg-Ca alloy by Al addition

We report the enhanced precipitation-hardening response of Mg-0.5Ca (wt.%) alloy by microalloying with Al. The peak hardness of 50 HV for the binary alloy was enhanced to 72 HV in a ternary Mg-0.5Ca-0.3Al alloy. Transmission electron microscopy and 3D atom probe analyses confirmed that the improvement in the peak hardness is associated with the dense precipitation of ordered monolayer Guinier-Preston zones and the subsequent formation of Al(2)Ca causes the over-aging. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.