Research On The Liquid Forging Process Of 7075 Aluminum Alloy Cover

Aluminum alloy materials have a series of excellent features such as low density and high strength,which will get good mechanical properties,physical properties and corrosion resistance through specific treatments.Different kinds of parts of the special vehicles are being converted to aluminum alloy materials.The forming method of liquid forging has the advantages of high-quality,low cost and remarkable manageability,in which the pouring process of molten metal is a key process link.The traditional pouring process is manual pouring along with many problems like high labor intensity and poor dimensional accuracy.In this paper,a quantitative feeding system of molten metal was designed based on a special vehicle cover,which achieved the quantitative transport of molten metal in a fully enclosed environment.There are lots of advantages of this new device including improving the accuracy of the molten metal pouring,reducing the oxide inclusions defects and increasing the quality of forming parts.The liquid forging mold of the special vehicle cover was designed based on the 2000 KN general hydraulic press,on which a pouring pipe was machining to associate with the quantitative feeding system of molten metal.The automatic extrusion casting of the special vehicle cover was completed through all these.The numerical simulation of the casing process was carried out based on the software Pro CAST,which optimized the processing parameters of the quantitative feeding device.The possible defects of the parts under different filling speeds were studied.The influence of the technological parameters such as the horizontal velocity of the punch was simulated and analyzed.The optimal horizontal velocity of the punch piston is 0.08m/s.The influence of the technological parameters such as the pouring temperature of metal solution,the preheating temperature of mold and the amount of shrinkage on the microstructure and mechanical properties of the formed metal was studied.The optimal pouring temperature of the molten metal is 720?~730?.The best mold preheating temperature is 200?~250?.The optimal amount of contraction is 3mm~4mm.The quality problems of the forming parts are summarized,such as cold separation,surface defects and internal shrinkage,which can be solved by increasing the packing time,controlling the temperature of the molten metal and the temperature of the mold and changing the mold lubrication.The structure and mechanical properties of the cover were analyzed.The structure of the flanges is relatively dense,the grain distribution is uniform.The bottoms of the covers are prone to shrinkage,and the mechanical properties are relatively low.The fractured morphology of the tensile specimen is analyzed.There are a lot of dimples and certain micro voids in the fracture.Some parts are distributed along the crystal fault.The fracture mechanism is mainly ductile fracture with a certain degree of cleavage fracture.