| Mg-Li alloy is the lightest metal structure material in engineering application at present, its general density is1.35-1.65g/cm3, and it has high specific strength and stiffness, its anisotropy is not obvious and low temperature performance is good. It has broad prospect of application in aerospace, electronics and military fields. But the Mg-Li alloy in applications is limited due to its lower strength, and creep resistance, corrosion resistance are both poor. This paper is based on Mg-Li-Al-Zn alloy, adding RE in Mg-12Li-2Al-2Zn alloy, study the influence of different adding contents of RE on Mg-12Li-2Al-2Zn microstructure and mechanical properties, and set the optimal RE adding amount of alloy as the research object, through homogenizing annealing and rolling process, explore the best preparation process of3C alloy sheet.Use testing equipments including the optics of metallographic microscope, tensile testing machine. X-ray diffraction and scanning electron microscopy (SEM) and energy spectrometer to analyze the influence of different RE additive amount on microstructure and mechanical properties of Mg-12Li-2Al-2Zn alloy. The results show that:Mixed RE has obvious grain refinement effect on Mg-Li-Al-Zn alloy. In the additive range of0.8%, with mixed RE content increases, the alloy microstructure is more uniform, and the grain refinement effect are more obvious; as additive amount of RE reaches1.2%, refined effect reduces. This best additive amount of RE in this experiment is0.8%. The main mechanism of refinement of mixed RE is the RE with surface activity is rich together in the growth interface of β-Li, restraining the growth of crystal.Study the influence of different homogenizing annealing time and different homogenizing annealing temperature on organization and performance of Mg-12Li-2Al-2Zn-0.8RE alloy. The results show that:the homogenizing annealing treatment can obviously improve the microstructure uniformity of Mg-12Li-2Al-2Zn-0.8RE alloy. Along with the annealing temperature increasing and the soaking time extending, particles in grains undergo process of separation, then getting together. The higher annealing temperature is, the more obviously diffusion does after particles on grain boundaries being decomposed, and the grain boundaries are more distinct. Ensure the best homogenizing annealing process system for Mg-12Li-2Al-2Zn-0.8RE alloy is200℃×12h.Explore the influence of different ways of rolling and annealing treatment after rolling on mechanics properties of Mg-12Li-2Al-2Zn-0.8RE alloy. The results show that:the microstructure of samples after unidirectional rolling process changes greatly, form slender fibrous tissue; particles are along the rolling direction dispersion distribution in grains and grain boundaries. After double-directionally rolling, samples have no fibrous tissue, and particles distribute uniformly in the alloy. Deformation strengthen can effectively change low intensity of Mg-12Li-2Al-2Zn-0.8RE alloy. After unidirectional and double-directionally rolling, which the deformations are both95.8%, and the alloy tensile strength of each sample respectively increases to248.9MPa and209.0MPa, compared with the alloy tensile strength of as-cast,92.4MPa. The comprehensive mechanical properties of plate samples after unidirectional rolling and double-directionally rolling through150℃×0.5h annealing are better, and unidirectional way rolling performances better than double-directionally rolling, its tensile strength and elongation were201.3MPa and27.2%. |
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