The Research On The Forming Process And Microstructure Defect Of Mg-based Bulk Amorphous Alloys

The advantages of Mg-based amorphous alloys are low density, high specific stiffness, high specific strength, good corrosion resistance, excellent ductility at room temperature, and it is the potential material for some special parts of aircraft, spacecraft and transport materials and so on. Mg-based bulk amorphous alloy prepared with strong glass forming ability, especially when master alloy prepared by high pressure casting, has high purity, fewer impurities, good surface quality of the filling and casting solidification, high production efficiency under the vacuum condition, and it is one of the most advanced method of Mg-based amorphous alloy forming method in the current.The experimental equipment used in this paper is the high vacuum directional solidification and arc melting and suction casting system which bought from the Chinese academy of sciences Shenyang scientific instruments co., Ltd, and has independently developed an adjustable vacuum side suction casting mold. The device after pumping vacuum, injecting argon as shielding gas in the furnace, arc melting the raw materials in the dry pot to prepared master alloy. Because of the protect gas injected in furnace, the mold is in the vacuum state, two sides of the dry pot have the different pressure, and the molten metal liquid impressed the mold by the rapid cooling process to prepare the amorphous alloy Mg54Cu26.5Ag8.5Gd11, the diameter reaches Φ20mm.Based on the above mechanism, this paper establishes the solid model by Creo, saves as the format of *.x_t, and is imported into ProCAST casting simulation software. In the MeshCAST module, sets up the process parameters of filling and casting solidification, and run the numerical simulate to obtain the simulation results.There are many factors that affect the casting process, which are not independent of each other. In this paper, we choose 4 main factors which affect the casting quality: pouring temperature, pouring pressure, heat transfer coefficient, mold temperature, and we choose 4 values in each factor. In the 4 level ranges of 4 factors, if the numerical simulation is carried out for each level and factor, the number of test design is much more huge. It is obviously very difficult to take a lot of manpower, material resources and time in the numerical simulation of such method. At the same time, when the conditions need to change sometimes, it may cause the test failure. To solve the above problems, and without affecting the simulation test results, this paper presents the design of orthogonal test, the selection of orthogonal table L₁6（4^4）, according to analysis the experimental results of the freezing time of the numerical simulation to reach the optimal process parameters in the fastest freezing time. The optimal parameters for the pouring temperature of 660 DEG C, pouring pressure of 800 bar（80MPa）, the heat transfer coefficient of 2500 W /（（m^2, K））, the mold temperature is 20 degrees centigrade.The research uses numerical simulation method to improve the traditional casting process. It not only extends the application of numerical simulation method in practical production, but also shortens the product development, production cycle, saves the production cost and improves the economic benefit.