新型mg-li-al-si合金制备及组织性能分析-preparation and microstructure and properties analysis of new mg - li - al - si alloy.docx

ABSTRACTWith the development of global industrialization and the traditional metal resources depleted increasingly, combined with the increasingly need of international environment for metal structure materials which are energy conservation, emissions reduction and weight-light. Magnesium alloy, as a lightweight structural material, the research on its development and application has become a hot spot. Mg-Li alloys are the lightest alloy materials, possessed of lots of advantages including high specific strength, high specific stiffness, good seismic performance and good high-energy particle penetration resistance, having drawn much attention from aerospace, weapon industry, nuclear industry, automobile, 3C and medical fields. Nervertheless, the application of Mg-Li alloys is also liminted because of their low absolute strength,poor corrosion resistance and poorhigh temperature creep properties. Therefore, many reseachers hope to improve the comprehensive performance of alloys by adding alloying elements in magnesium lithium alloy or other hot working processes.This study is based on the relatively mature Mg-9Li-3Al alloys, Mg-9Li-3Al-xSi alloys with different contents of Si were prepared by “mixture method”. The microstructure and mechanical properties of the as-cast and as-extruded alloys were investigated by optical microscopy(OM), scanning electronic microscopy (SEM), X-ray diffraction(XRD) and mechanical properties testing. Meanwhile, the thermal deformation behavior of as-cast Mg-9Li-3Al-0.5Si alloy was studied by hot compression testing. Then the heat treatment process on the properties of as-extruded alloy was studied. The specific results are as follow:① The as-cast Mg-9Li-3Al alloy is consist of α-Mg, β-Li, Mg17Al12 and a little ofAlLi phase. With the addtion of Si into alloys, the microstructure of the alloys were refined clearly, the amount of α-Mg phase reduced, the Mg17Al12 and AlLi phase were replaced by Mg2Si phase. But if the content of Si is too h