Effects of Cu addition on the microstructure and hardness of Mg-5Li-3Al-2Zn alloy

The effects of Cu additions (0.5-2.0 wt.%) on the microstructure and hardness of Mg-5Li-3Al-2Zn alloy were studied. Optical microscope, scanning electronic microscope, X-ray diffraction and energy dispersive X-ray spectroscope were employed to study the microstructure of the alloys. Results show that, as the Cu addition increases, the AlCuMg phase exists in the alloy. This phase can partially restrain the formation and growth of AlLi phase. The Brinell macrohardness of the as-cast alloys increases with the increase of Cu content. The Vickers microhardness of the phases of as-cast alloy was measured to analyze the strengthening mechanisms.