| Mg-Li series alloys are kinds of new alloys with smallest density so far. The plastic formability of Mg-Li series alloys is better than that of other series magnesium alloys. The ultralight Mg-Li alloys have wide application in aerospace, defense, automobile and electronic fields because of their low density, high specific strength, high specific stiffness, good damping capacity, excellent reducing vibration properties and excellent resistance to high-energy particles.In this paper, Mg-Li-Al alloys were selected as the object, the effects of Al-Ti-C master alloy, Al-Ti-C-Gd master alloy and Nd on the microstructure and mechanical properties of Mg-8Li-3Al alloys were investigated. Meanwhile, base on experimental collection of the contents of Mg, Li, Al and tensile strength and elongation of representative Mg-Li-Al alloys, a neural network model was established. The results are showed bellow:The Al-Ti-C and Al-Ti-C-Gd master alloy were prepared by a liquid-solid reaction can effectively refine α phase of Mg-8Li-3Al alloy. Al4C3and TiC particles can act as heterogeneous nuclei for α-Mg, Al-Gd compounds distribute at the phase boundary can restrict the growth of α-Mg. When the addition amount of Al-Ti-C master alloy is1.0wt%, the morphology of α-phase dendrites changes into lumps, the sizes of α-phases are reduced the microstructure are roundness. The tensile strength and the elongation of Mg-8Li-3Al alloy are improved from175.64MPa to199.28Mpa, and the elongation is improved from13.80%to14.60%. respectively. When the addition amount of Al-Ti-C-Gd master alloy is3.0wt%, the size of a-phase is smallest and the microstructure of a-phase is roundness. The tensile strength and elongation were185.90MPa and24.60%, increased by5.8%and78.2%, respectively.The addition of Nd in Mg-8Li-3Al alloy can refine a phase. With the Nd addition, the amount of a phase is reduced, Al combines with Nd to form Al2Nd and the Al2Nd compound mainly distributes at the phase boundary and inside the β phase. When the addition of Nd is1.6wt%. the size of a phase is the smallest. Further increasing the amount of Nd to2.0wt%, partial α phase becomes long ribbon shape and the size of Al2Nd becomes larger. The refining mechanism mainly owes to the increasing constitutional supercooling at the solidification front and Al2Nd phases distribute at the phase boundary and inside β phase can also restrain the growth of α phase. Nd can also improve the tensile strength and elongation of Mg-8Li-3Al alloy. When the addition of Nd is2.0wt%, tensile strength reaches185.95MPa, when Nd is1.6wt%, elongation is16.30%.BP and PSO-BP neural networks were proposed to predict the tensile strength and elongation of Mg-Li-Al alloys. The PSO-BP network model can describe the quantitative relationship between the Mg-Li-Al alloy’s composition and its mechanical properties. The prediction of the influence of Al addition on the mechanical properties of as-cast Mg-Li-Al alloys is consistent with the related experimental results. It is possible that the mechanical properties can be predicted without experiments by inputting alloy compositions into the trained network model, and the lowest cost on the experimental requirement can be achieved. |
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