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Structural materials, magnesium alloy is the lightest structural materials, its excellent properties, such as excellent thermal performance, high vibration capability, good damping properties and electromagnetic shielding performance has been widely used in the automotive industry, aerospace as well as the field of electronic communications. But low as magnesium alloy absolute strength, poor corrosion resistance, ductility and poor reasons, restricting its large-scale application. The composition of the magnesium alloy design and optimization, as the basis of the development of magnesium alloy technology, you can provide theoretical and experimental evidence for the development of new magnesium alloy. Therefore, the design, optimization has good mechanical properties of magnesium alloys is very necessary. Our group recently developed a better plastic cast magnesium alloy AT33 and AT63. Which stretch AT33 alloys at room temperature exhibit good ductility up to 35% elongation, tensile strength of 207-248 MPa; stretch AT63 alloys at room temperature, the tensile strength of 271-300 MPa, extending rate of 16-18%. Comprehensive study of this alloy to the ternary alloy of Mg-Al-Sn-based, to study changes in the nature of the strength, ductility, and Brinell hardness of the different components of the alloy by a different ratio of the two alloy elements, Al and Sn , and by means of OM, SEM and EDS analysis of theoretical and experimental means to detect 27 different component alloy cast microstructure in order to optimize a number of cast magnesium alloys have excellent mechanical properties, for the development and application of new alloy basis. The main findings are as follows: (1) revealed the cast structure of Al, Sn content of magnesium alloy Mg-Al-Sn. When the Sn content is 1wt%, 2 wt%, 3 wt.%, The Al content of from 1 wt.% To 9wt.%, The dendrites of the alloy from the initial gradually transformed into a uniform equiaxed crystal grains gradually refined grain boundary precipitation phase growing. When the Al content are 1wt.%-9wt.%, Sn content of from 1 wt.% Increase 3wt.%, The alloy grain refinement. AT32 and AT33 alloy grain boundaries is wide, and some of the compound phase in the grain boundary precipitates. AT62 and AT63 alloy grain boundaries on the distribution of a large number of discontinuous compound phase. AT81 and AT82 alloy grain boundary distribution mesh compound phase. And, as the Al content increases, the intragranular and the Al content in solid solution in the grain boundary is increased accordingly. (2) revealed the influence of Al, Sn content on the mechanical properties of magnesium alloy Mg-Al-Sn. When the Sn content is 1wt%, 2 wt%, 3 wt.%, The Al content of from 1 wt.% To 9wt.%, An ultimate tensile strength of the Mg-Al-Sn-based magnesium alloy rendering first increased and then decreased The trend of the yield strength of the trend presents elevated, the elongation at break increased at first and then a downward trend. When the Al content are 1wt.%-9wt.%, In the low aluminum and the aluminum component in the alloy, the ultimate tensile strength, yield strength with increasing Sn content increases, elongation showing elevated downward trend. With increasing Sn content in the the Alumina composition alloy, the ultimate tensile strength, yield strength and elongation at break, there is a downward trend. When the Sn content is 1wt%, 2 wt%, 3 wt.%, The Al content of from 1 wt.% To 9wt.%, A Brinell hardness of the alloy increases; When the Al content types is 1 wt.%-9wt.% , Sn content is from 1 wt.% increase 3wt.% on the Brinell hardness of the alloy has little effect. Mg-Al-Sn system magnesium alloy tensile fracture type ductile fracture, fracture mechanism is transgranular fracture and intergranular fracture caused by the second phase particles mixed fracture. (3) preliminary optimization of the the several good mechanical properties of the alloy. When the Al content is up to 3 wt.% Sn content of 2wt.%, 3wt.%, The alloy exhibit a good plastic properties, elongation at break of up to 39%. When the Al content is reached 8wt%, Sn content of 1 wt.%, 2 wt%, the alloy has a higher tensile strength properties, the ultimate tensile strength of up to 280MPa. When the Al content of 6 wt% Sn content reached 2 wt.%, 3wt.%, The alloy has excellent mechanical properties, ultimate tensile strength of 260MPa, elongation at break of up to 30%. When the Al content reach 9wt%, the Brinell hardness values ??of the alloy reaches the maximum.
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