Study On Preparation Of Aluminum Alloy Semi-solid Slurry By Internal Cooling Method

The semi-solid slurry of Aluminum alloy was fabricated by a bran-new technology-internal cooling method which was studied in this paper. We adopt the internal cooling for preparation of aluminum semi-solid slurry by reason that the aluminum alloy has the low melting point of the aluminum alloy, a wider solidification temperature range, good casting properties and high mechanical properties, which can be strengthened by heat treatment.The main content of this thesis includes two aspects as follow:This paper studied the preparation of semi-solid aluminum alloy slurry by internal cooling method.(1) A356aluminum alloy was studied in experimental Ⅰ. The semi-solid slurry of A356aluminum alloy was fabricated using of the internal cooling method. On the basis of systematic experiments, we use the way to control variables to collect the mold temperature curve within crucible, explore and master the internal cooling process conditions, and observe the microstructure on the solidification of the aluminum alloy.(2)The master alloy of different components of Al-Cu system was prepared in Experiment Ⅱ, which studied as an object. We use internal cooling method of the alloy melt, and put the as-prepared Al-Cu alloy were added into the same component by the calculated temperature of the Al-Cu alloy melt in stirring. That is say that Al-Cu alloy semi-solid slurry was prepared by internal cooling system. using the perturbation of the temperature of the internal cooling method to obtain the semi-solid slurry with homogeneous microstructure. The five alloy composition as the following: Al-5%Cu, Al-10%Cu, Al-15%Cu, Al-20%Cu and Al-25%Cu.In this paper, characteristics of the solid-liquid mixed casting and semi-solid process, a bran-new technology was proposed as the internal cooling method to prepare excellent semi-solid alloy slurry. The process parameters that affect coagulation organizations were discovered, which include vibration conditions and cooling conditions. These research indicate:The casting temperature d-value ratio in vibrating is lower than none-vibrate and the casting grain is to be more better and uniform; The crystal grains are finer and closer to spherical with rapid cooling; as-prepared aluminum alloy was dissolved and stirred resulting convection, which can change the conditions of thermodynamic and kinetic conditions of the crystal growth, the grain growth in the forefront of the solid-liquid interface temperature field and concentration field was tending to uniformity, eliminate the segregation in resulting isotropic growth appeared, broken dendrite crystal, and the nucleation rate increased, while increasing under-cooling and getting grain refinement; As the same solid fraction of Al-Cu hypoeutectic alloys, the more increasing Cu content, the finer grains; As the same ingredients of Al-Cu alloy and the same starting temperature under stirring, the smaller the solid fraction, the finer grains.