New Ultra-light And High-strength Mg-Li Alloy Design

Mg-Li alloy has the advantages of low density,high specific strength and anti-vibration and noise resistance.It can increase the effective load and reduce energy consumption.In this paper,the target alloys were prepared by means of stirring casting for exploring methods such as alloying,adding reinforcement particles and thermomechanical deformation to design a Ultra-light and high-strength Mg-Li alloy.At the same time,the alloys were solid-solution treated on this basis to further improve the mechanical properties of the alloy.In addition,aging treatment was performed on the alloy after solution treatment to test the high temperature performance stability of the alloy.The alloys prepared in this paper are mainly Mg-8Li-3Al-x TiC(x=0,0.4,0.8,1.2),Mg-8Li-3Al-2Sn-x Y(x=0,0.5,1.0,1.5)and the alloy prepared by adding nano-TiC particles and Y to the Mg-8Li-3Al-2Sn alloy in the optimal addition amount obtained from the study.The microstructure and mechanical properties of the alloy were explored.The phases in the Mg-8Li-3Al alloy include?-Mg,?-Li,and Mg Li Al₂.The tensile strength and yield strength of the as-cast Mg-8Li-3Al-x TiC alloy increased first and then decreased while the elongation continued to increase.Among them,the as-cast Mg-8Li-3Al-0.8TiC has the best mechanical properties.The changing law of strength and elongation is consistent with the as-cast state.The mechanical properties of the extruded Mg-8Li-3Al-0.8TiC alloy are the best.The Mg-8Li-3Al alloy was added with 2wt%Sn to make the Mg-8Li-3Al-2Sn alloy.The phases in the alloy are mainly?-Mg,?-Li,Mg Li Al₂ and Li₂Mg Sn.Adding the incompatible content Y(0wt%,0.5wt%,1.0wt%,1.5wt%)to the Mg-8Li-3Al-2Sn alloy,the addition of Y makes the alloy have more Al₂Y phases which are white granular phase and are distributed in the?-Mg phases and?-Li phases.When the amount of Y added is 0.5wt%,the as-cast Mg-8Li-3Al-2Sn-0.5Y alloy has the best mechanical properties.The as-cast alloy is subjected to hot extrusion deformation at an extrusion ratio of 16:1 and an extrusion temperature of 250?.The mechanical properties of Mg-8Li-3Al-2Sn-0.5Y are similar to those of the as-cast alloy while the elongation rate is higher.When the amount of Y added is 0.5wt%,the mechanical properties of the extruded Mg-8Li-3Al-2Sn-0.5Y are the best.However,the strength difference of the extruded alloys with different Y content is very small,and the strength rise and fall are small.The strengthening effect of rare earth Y is largely hidden by the extrusion deformation strengthening.0.8wt%TiC and 0.5wt%Y were added to the Mg-8Li-3Al-2Sn alloy.At this time,the phases in the alloy are mainly?-Mg,?-Li,Li₂Mg Sn,Al₂Y,TiC and Mg Li Al₂.The tensile strength and yield strength of the obtained Mg-8Li-3Al-2Sn-0.5Y-0.8TiC as-cast alloy are higher than those of Mg-8Li-3Al-0.8TiC and Mg-8Li-3Al-2Sn-0.5Y.The elongation is lower than Mg-8Li-3Al-0.8TiC and is similar to Mg-8Li-3Al-2Sn-0.5Y.The alloy was subjected to hot extrusion deformation with an extrusion ratio of 16:1and an extrusion temperature of 250°C.The tensile strength,yield strength and elongation of the obtained Mg-8Li-3Al-2Sn-0.5Y-0.8TiC alloy are slightly higher than the Mg-8Li-3Al-0.8TiC alloy and Mg-8Li-3Al-2Sn-0.5Y alloy.The effect of TiC and Y composite strengthening of Mg-8Li-3Al-2Sn alloy is better.The Mg-8Li-3Al-2Sn-0.5Y-0.8TiC alloy was solution treated at 300?and 350?for 6 hours.The tensile strength and yield strength of the as-cast Mg-8Li-3Al-2Sn-0.5Y-0.8TiC alloy after being solution treated at 300°C and 350°C showed an increasing trend while the elongation showed a decreasing trend.The tensile strength,yield strength and elongation of the extruded alloy Mg-8Li-3Al-2Sn-0.5Y-0.8TiC showed a slight decreasing trend after being solution treated.After the Mg-8Li-3Al-2Sn-0.5Y-0.8TiC alloy was solution treated at 350?,the aging treatment was carried out at 100?×24h and 150?×24h.The alloy appeared aging softening and the the Al Li phases dissolved in the alloy renewed a large amount of precipitation,distributed in a network on the edge of?-Li phase and?-Mg phase.