Effects of electromagnetic field on structure and heat treatment behavior of Mg-Li-Al alloys
(School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China)
Abstract: The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied. Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for solution treatment and aging treatment. Experimental results show that the dendritic arms are broken and a large quantity of equiaxed grains appear in the microstructure of specimens with electromagnetic stirring (EMS). With the increase of the quenching temperature(150-350 ℃), the solution of Mg and Al in solid β phase increases, and the Brinell hardness of the alloy increases as well. Aging peak and over aging happen because θ(MgLi2Al) which precipitates in the β matrix and strengthens the alloy is unstable and transforms to stable AlLi phase. Aging curves of EMS specimens change in a smaller amplitude.
Key words: Mg-Li-Al alloys; electromagnetic stirring (EMS); solution treatment; artificial aging; hardness