Study Of Microstructures And Mechanical Properties On α-based Mg-Li Alloys With Cd/Sn Alloying

Because of the low density, high specific strength, high stiffness, good damping capacity and good electromagnetic shielding properties, etc., Mg-Li alloys have received wide attention in the fields of aerospace, electronics industry and other areas.However, The application of Mg-Li alloys is limited due to the lower strength and poor corrosion resistance.The goal of this paper is to obtain high-performance wrought Mg-Li alloys.The effects of Cd, Sn on the microstructure and mechanical properties of theα-based Mg-5Li-5Al-3Zn alloys with the addition of Cd, Sn were studied by using vacuum melting, optical microscopy, scanning electron microscopy, X-ray diffraction, Energy Dispersive Spectrometer (EDS, tensile test machine,et al. And its mechanism is revealed.The influences of extrusion on the microstructure and mechanical properties of as-extruded Mg-5Li-5Al-3Zn alloys with the addition of Cd, Sn alloys were investigated by microstructure analysis and tensile properties tests.The microstructure evolutions of the Mg-5Li-5Al-3Zn alloys with the addition of Cd, Sn during the process of extrusion were studied and the mechanisms of Dynamic recrystallization and thermal extrusion deformation were analysised.The results show that Cd & Sn are both able to refine the grains of the Mg-5Li-5Al-3Zn alloys and weaken the intercrystalline segregation of the AlLi phase at the grain boundary. Cd & Sn also can promote the AlLi with mesh structure changes to be intermittent state and precipitates insideαphase. The Cd elements are mainly solid solute in a phase and led to AlLi phase distribute evenly with refiner size. The effects of Sn added in Mg-5Li-5Al-3Zn alloy on the AlLi are similar to Cd.The solid solubility of Sn is small in Mg. Sn can form Mg2Sn particles with Mg.These particles distribute evenly in grain boundary, play the role of dispersion strengthening.The phases have no change after homogenization treatment of Mg-5Li-5Al-3Zn-xCd/Sn alloys. The density of AlLi is decreased at the grain boundary and the distribution of AlLi phase is more uniform in the matrix alloys. The mechanical properties were greatly improved and the grains get further refinement after hot extrusion deformation of Mg-5Li-5Al-3Zn-xCd/Sn alloys. During the hot extrusion deformation process, there is the occurrence of dynamic recrystallization.In addition, the Mg-4.60Li-4.84Al-2.76Zn-1.87Cd alloy with 1.87wt.% Cd show the best mechanical properties with the highest strength of 288MPa, a relative good elongation of 14%.The properties of Mg-5.32Li-5.22Al-3.04Zn-1.80Sn alloy is comprehensive when the Sn content is 1.8 wt.%. Its strength is 290MPa, and elongation is 21%. The rolling after extrusion can further improve the tensile strength but the ductility.Dislocation slip is the deformation mechanism of alloys in plastic deformation processing. Recrystallization is the main deformation features of the alloys and recrystallization mechanism is continuous dynamic recrystallization. The results of the strengthening due to the combined effects of solution strengthening, grain refinement, the second phase strengthening and strain-hardening.The alloys with addition of Cd are mainly dominated by solution strengthening.While alloys with addition of Sn are mainly dominated by the second phase strengthening.