| With the advantages of low density, high specific strength, good shock resistance, strong ability of electromagnetic shielding, Magnesium alloy is highly valued by the aerospace, defense industry and other fields. It is the new trend of the development of light metal materials around the world. Because of the strength of magnesium alloy is low(less than 280MPa), poor plasticity(less than 10%), poor corrosion resistance, limiting its scope of application. These reasons are: smelting, molding, surface treatment and many other problems. In this paper, through the improvement of smelting, optimization of process, t o search for a new series of Al-Zn magnesium alloys, then on this basis, using two kinds of tombarthite elements La and Ce, two kinds of other elements Ti and Sn to improve the mechanical properties by micro-alloying. In the end, analyze the impacts of La, Ce, Ti and Sn on the micro-structure and mechanical properties of AZ46 magnesium alloy.Smelting equipment is composed of five parts, they are: the furnace, intermediate frequency power supply, pneumatic, gas mixing, protective gas furnace cover and casting. The main advantages of this equipment are as follows:(1)The equipment is composed of a power supply control cabinet and melting furnace, wet and dry areas are separated, high and low temperature areas are separated;(2)The heat source is medium frequency power supply, medium frequency power supply has advantages of quick heating, uniform, high efficiency, strong controllability;(3)The crucible is made of 321 stainless steel, for its high temperature resistance, high strength and reducing the polluting to magnesium alloy, its shape is straight type and convenient to disassemble and clean;(4)Because of the protective gas furnace cover, reducing the leakage of protective gas and air entering into crucible as far as possible;(5)Equipment has a baffle in the crucible of drainage hole, similar to the design of the "teapot mouth", the advantages are removing the bezel easily and cleaning the crucible easily.In the melting process, Ar gas and CO2 gas are used as protective gas, the volatilization and oxidation of melting magnesium alloy has been well suppressed, two kinds of gases play their own characteristics. Considering the protection of the effectiveness and cost, the decisions are as follows: Ar is 5.0L/min, CO2 is 2.0L/min, while the preheating and insulation stage reducing to 50% and 80% can play a protective role.Using AZ46 magnesium alloy as matrix, on the basis, adding La, Ce, Ti and Sn four kinds of alloy elements, combining with energy spectrum scan test, metallographic observation and the mechanical property test, analysis the influence of micro-structure and the properties to AZ46 magnesium alloy. The conclusions are as follows:(1) Tombarthite elements La and Ce are added into the AZ46 matrix, it is unknown that the two elements whether dissolved into the matrix or not, and the strength and elongation AZ46-Ce AZ46-La decreases slightly, but the casting hardness increases, it also provides a way to improve the hardness of magnesium alloy;(2) Ti and Sn are added in the AZ46 matrix, It is difficult for Ti element to dissolve in the matrix, but the melting point of Ti is high,it can be used as heterogeneous nucleation sites for grain refinement, and improves the strength of matrix; Sn element is dissolved into the matrix, and reacting with Mg forms spherical Mg2 Sn, it can improve the mechanical properties of AZ46 magnesium alloy;(3)When both Ti and Sn are added to AZ46 magnesium matrix, casting hardness and strength increases significantly, elongation rate decrease slightly, under the collaborative action of Ti and Sn, AZ46 magnesium matrix mechanical properties are obviously improved, using the equipment and in the conditions of the simple processing, the tensile strength is 369 MPa, elongation rate is 15.5%. |
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