Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The inf...Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The influences of the slow shot speed, the fast shot speed and the biscuit thickness on the externally solidified crystals （ESCs） were investigated. With the increase of the biscuit thickness, the number of the ESCs in the cast samples decreases. Under a low slow shot speed, larg ESCs are found in the cast structure and a high fast shot speed results in more spherical ESCs. The relationships between ESCs and process parameters were also discussed.展开更多
Production of A6063/SiC-B4C hybrid composite using vacuum assisted block mould investment casting was investigated. Firstly,SiC-B4C hybrid preforms were fabricated in cylindrical shape.The preferred mean particle size...Production of A6063/SiC-B4C hybrid composite using vacuum assisted block mould investment casting was investigated. Firstly,SiC-B4C hybrid preforms were fabricated in cylindrical shape.The preferred mean particle size of the SiC and B4C powders were 60μm and 55μm respectively.In early experiments,single powder ratio of 85%SiC and 15%B4C was selected to produce the tough preforms.Subsequently,the preforms were placed into the cylindrical shape gypsum bonded block investment moulds and A6063 alloy was infiltrated into the preforms using vacuum assisted（-10 5 Pa）casting machine.Porosity fraction of preforms was determined using Archimedes’test.The fabricated cast specimens were characterized using hardness tests,image analysis and SEM observations and EDX analysis.The result indicates that,by the vacuum assisted block mould investment casting technique,the infiltration of the preforms by molten metal was successfully realized.展开更多
Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in castin...Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.展开更多
基金Project(2009AA03Z114)supported by the National High-tech Research and Development Program of ChinaProject supported by Tsinghua-Toyo R&D Center of Magnesium and Aluminum Alloys Processing Technology
文摘Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The influences of the slow shot speed, the fast shot speed and the biscuit thickness on the externally solidified crystals （ESCs） were investigated. With the increase of the biscuit thickness, the number of the ESCs in the cast samples decreases. Under a low slow shot speed, larg ESCs are found in the cast structure and a high fast shot speed results in more spherical ESCs. The relationships between ESCs and process parameters were also discussed.
基金Yildiz Technical University and Balkan Center for Advanced Casting Technologies (BCACT) for their financial support
文摘Production of A6063/SiC-B4C hybrid composite using vacuum assisted block mould investment casting was investigated. Firstly,SiC-B4C hybrid preforms were fabricated in cylindrical shape.The preferred mean particle size of the SiC and B4C powders were 60μm and 55μm respectively.In early experiments,single powder ratio of 85%SiC and 15%B4C was selected to produce the tough preforms.Subsequently,the preforms were placed into the cylindrical shape gypsum bonded block investment moulds and A6063 alloy was infiltrated into the preforms using vacuum assisted（-10 5 Pa）casting machine.Porosity fraction of preforms was determined using Archimedes’test.The fabricated cast specimens were characterized using hardness tests,image analysis and SEM observations and EDX analysis.The result indicates that,by the vacuum assisted block mould investment casting technique,the infiltration of the preforms by molten metal was successfully realized.
基金Project(50975093)supported by the National Natural Science Foundation of ChinaProject(08-0209)supported by New Century Excellent Talent in University,Ministry of Education,ChinaProject(2009ZM0283)supported by the Fundamental Research Funds for the Central Universities,China
文摘Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.
