Research On The Clad Cast Technology Of7A52/7B52Super-high Strength Aluminum Alloy

As a commonly used material in aerospace and military equipment,7xxx series aluminum clad sheets are mainly produced by means of rolling cladding at present. However, these sheets usually have low bonding strength in the interface and poor comprehensive performances so that some requirements for special properties cannot be met easily. The production of clad casting ingots by semi-continuous casting technology is a new process, which overcomes the shortcomings of the traditional composite technology:multiple operations, high labor intensity, poor combining strength, high cost of production, etc. As a promising technology, it lowers the manufacturing costs and shows promising prospects.The present work mainly aims at the application of casting composite technology in the7series aluminum alloy. The casting equipments and process for the production of7A52/7B52clad ingots are studied. First, the surface morphology, macro-and microstructures of the ingots produced under different conditions were investigated and analyzed; next the effects of various processes on the structures in the composite interface were discussed; then the distribution and diffusion of the corresponding elements near the interfaces are compared by SEM analysis; finally the mechanical properties of the clad ingots were studied. The results are summarized up as follows:(1) The effects of casting temperature, casting speed, contacting height and cooling intensity of the cooling plate on the casting process were analyzed. Finally, hot-top graphite ring mold is designed as the equipment suitable for casting clad ingots.(2) Through the analysis of the experimental results of different technologies. The optimal casting parameters of7A52/7B52two-layer clad ingots were obtained as follows:the casting temperature of7A52alloy and7B52alloy is730℃, the casting speed is40mm/min, and the contacting height and water flow of the cooling plate are40mm and8L/min, respectively.(3) The measuring temperature field agrees well with the corresponding simulation result. (4) A good homogenization effect is obtained when the heating temperature is450℃and holding time24h for the clad ingot. Under such conditions, the constituents with low melting point in the alloy are not burnt, and the non-equilibrium constituent phases in the alloy with high melting point are dissolved sufficiently.(5) The thicknesses of Zn and Mg diffusion layers in the composite interfaces are obtained based on the SEM analysis for the clad ingots. The results show that the thickness of the layer in the as-cast sample is about15μm and the homogenized sample is about20μm. The bonding strength of the interface is greater than217MP.