| This paper based on the research and present application at home and abroad situation improved the semi-solid slurry making device of vibrated sloping plate. Taking the A356 alloy as the research objects, It analyzed the law of heat transfer and formation mechanism of microstructure, researched the effect of technologies on the microstructures and properties of semi-solid slurry making, Semi-solid Rheo-rolling and heat treatment. The main work and results are as follows:(1) It analyzed the forming mechanism on the sloping plate, calculated nucleation rate of the slurry which is similar to the result of Turnbull. There are three mechanisms working together to form the non-dendrite microstructure:?Heterogeneous nucleation on the surface of sloping plate; ?Eruptive nucleation in the melt with homogenous solute distribution; ?Flow shearing of Melt and vibration of sloping plate cause dendrite microstructures to be fractured.(2) It got the effect law of technologies included casting temperature, Angle of Inclination, vibration conditions and cooling intensity on the semi-solid microstructure of A356 alloy:?From 100 mm to 600 mm in length, as the length of sloping plate increases, microstructures of semi-solid become smaller and rounder; ?At the Angle of 45°and the temperature of 630? to 680?, with the reduction of pouring temperature, get into groups of solid increases, the average grain size decreases, the grain changes smaller and rounder, but the vibration is weaken when the pouring temperature is too low; ?As the voltage increases, the fistly increases and then decreases. When the vibration frequencies range from 0 to 80 Hz, the microstructures become better with the increase of it. And when it is higher than 80 Hz, the microstructures gradually become worse; ?The intensity of sloping plate is increased and the solid fraction of the microstructures is increased Which becomes uniformer and smaller. Under the condition of this experiment, the best technologyies of making the semi-solid slurry of A356 alloy are:sloping plate is a flat plate of copper with runner way,the casting temperature is 640?650?, the vibration voltage is 15V, the vibration frequency is 80Hz,and the flow rate of cooling water is 0.05m3/min.(3) It combined the method of slurry making by sloping plate with roll-casting process into a successful preparation of A356 belt whose cross section width was 200 mm and thickness was 0.5?5mm and improved the plasticity of A356 alloy by Improving the traditonal roll-casting process. Under the condition of this experiment, the best technologyies of sheet processing of A356 alloy are:the casting temperature is 650?660?, the thickness is 0.8mm, the linear speed of working roll is 0.069m·s-1, the vibration voltage is 15V, the vibration frequency is 80Hz. The tensile strength, elongation and hardness of A356 sheet are 248 Mpa,9.1% and 83HV which are better than that of the casting products.(4) The sheet of A356 alloy was disposed by solution and aging, whose microstructures and comprehensive mechanical properties were improved. Its comprehensive mechanical properties is that:the tensile strength of 265 MPa, the elongation of 16.5%. The effect of heat treatment on microstructures and properties of the A356 sheet was analysised. When the solution temperature is respectively 535? and 550?, the tensile strength, elongation and hardness are fistly enhanced and then lessened As the extension of time, which respectively reach the best value at the time of 4.5h and 3h. The tensile strength, elongation and hardness of the sheet are 252MPa,18% and 88HV after 535?×4.5h solution treatment; The tensile strength, elongation and hardness of the sheet are 260MPa,14.8% and 92HV after 550?×3h solution treatment; The comprehensive mechanical properties respectively reach the best value at the time of 5h and 2h, which are265Mpa,16.5% and 260Mpa,15.1%. Under the condition of best technologies, the dimple in the fracture is big and deep, which declarates that the ductility is good. |
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