Numerical Simulation Research On Clad Casting Of7XXX Aluminum Alloys

Bi-metal Composites are urgently needed materials in military, aerospace, exploration, civilian industries, etc., which have also become preferential projects in national development of new materials. In the present work, based on the development needs of aluminium composites in our country, clad casting technology was deeply studied. This work mainly aims to investigate the effects of casting equipment and technics on the metallurgical qualities and casting process stabilities of the composite ingots and to obtain composite ingots with clear and straight interfaces that are free of porosities and inclusions and possess high bonding strength (metallurgical bonding).In this work, a numerical model was built to describe the clad casting using the FLUENT software included in the Finite Element Analysis software. Based on the corresponding numerical simulation, the temperature field, flow field and heat transfer in the300mmx500mm7A52/7B52two-layer clad ingots were studied. Meanwhile, the effects of split flow pattern, distribution of secondary cooling water, position of graphite plate, casting temperature, casting speed and amount of secondary cooling water on the temperature and flow fields in the clad casting were analyzed.Through the simulation calculation, equipment parameters suitable for the300mmx500mm7A52/7B52two-layer clad ingots were obtained as follows:1. to ensure uniform temperature distribution in the composite interface, the splitter box should be narrow and close to the edge of the ingots;2. to alleviate the low temperature in the three-dimensional cooling zone, the secondary cooling water holes are plugged successively;3. to guarantee uniform temperature distribution in the solid support layer, the lower edge of the graphite plate should be20mm lower than the upper edge of the graphite ring.Moreover, effects of the casting technics on the temperature distribution in the interface were acquired as follows:1. in the range of953-993K, the temperature in the composite interface is slightly raised with increasing the pouring temperature;2. the sump depth and reheat temperature are increased with increasing the casting speed or lowering the amount of the secondary cooling water. In addition, the casting techinics parameters for a suitable temperature in the interface are determined as follows:the pouring temperature is973K, the casting speed45mm/min and the amount of the secondary cooling water90L/min.Based on the equipment and technics parameters determined by the simulation results, clad casting was carried out. The results showed that the interfaces in the composite ingots are clear and straight and free of porosities and inclusions. Furthermore, the Zn and Mg elements at the two sides of the interface are interdiffused to some extent, which proves that a metallurgical bonding is obtained.