| The variety, shape, quantity and distribution of alloy phases in Mg-Al-Zn system wrought magnesium alloys with aluminum content higher than 11% in the states of casting, extruding, solid solution and aging strengthening were investigated by using OM, SEM and XRD, respectively. The effect of the different content of Al and Zn on the microstructure and mechanical properties of magnesium alloys was investigated. Based on the above-mentioned results, the effect of Si and Ca addition on the microstructure and mechanical properties of wrought magnesium alloys was also studied. The main conclusions are presented as follows.(1) The best extruding parameters such as the temperature 300℃, the heating time 3h, the extrusion ratio 17.4 and the extrusion velocity 0.8m/min were obtained by analyzing the all factors effect.(2) For as-extrusion wrought magnesium alloys, the max tensile strength can be obtained is 371.8MPa when the content of Al is 20%, while the elongation is only 1.2%. As the results suggest, Mg-11Al-3Zn-0.4Mn alloy has the best synthetically mechanical property. The maximum value of the tensile strength can reach 353.0MPa, and that of the elongation 11.4%.(3) When the element Si content was 6%, the tensile strength of Mg-11Al-3Zn-0.4Mn-0.7Ca-xSi alloy reached max amount which is 336.8MPa, 4.6% less than Mg-11Al-3Zn-0.4Mn. The element Ca could refines the microstructures of as-extrusion wrought magnesium alloys, and improves its tensile strength. The max tensile strength of Mg-11Al-3Zn-0.4Mn-0.7Ca is 362.7MPa that is 2.7% increment compared to that of Mg-11Al-3Zn-0.4Mn alloy.(4) Mg-11Al-3Zn-0.4Mn as-extrusion wrought alloys were heat-treated by using several different treatments. During the course of T4 treatment, the elongation of magnesium alloys peaks at 12.5%.; During the course of T5 treatment, the tensile strength of alloys peaks at420.3MPa; During the course of T6 treatment, the tensile strength and the elongation were 365.1MPa and 8%.
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