Precipitation in Mg-(4-13)% Li-(4-5)% Zn ternary alloys

Abstract

Precipitations in Mg-Li-Zn ternary alloys containing 4 to 13% Li and 4 to 5% Zn (in mass%) with α or β single phase, or with (α + β) dual phases were investigated using a micro-Vickers hardness measurement and transmission electron microscopy. Age hardening in the α phase alloy was found to occur, which was attributed to the precipitation of the stable θ (MgLiZn) phase with the following orientation relationships: [1010]α ∥ [110]θ, (0001)α ∥ (111)θ. In the (α + β) phases alloy, the precipitation of the α phase together with the metastable θ′ (MgLi2Zn) phase occurred at grain boundaries between the α and β, and also β and β grains. The orientation relationships between the α and θ′ were as follows; (0001)α ∥ (011)θ, [0110]α ∥ [111]θ′. Age hardening in the β alloy was caused by the precipitation of the θ′ phase and over-aging was attributed to the precipitation of the α and θ phases.