Research On Heat Treatment And Granule Medium Forming Technology Of AA6061 Tube

The high strength aluminum alloy tube and sheet can not be formed in complex parts for high strength and poor plasticity at room temperature.Warm forming processes of aluminum alloy tube and sheet have became a research focus for the elongation of high strength aluminum alloy increases significantly by the elevation of forming temperature.However,the control requirement of exact forming temperature and the demand of parts with high temperature resistance,make process control difficult and processing cost high.Based on this point,this thesis puts forward the technological process of solution treatment — granule medium internal high pressure forming — aging treatment.In order to establish a processing method of high strength aluminum alloy with the advantages of convenient implementation,low requirement to equipment and flexible design in product,the technology of granule medium internal high pressure forming is applied in the tube forming and the mechanical properties of the tested alloy is changed before and after deformation by heat treatment.In this paper,the AA6061 extruded tube is investigated to research the effect of solution treatment on mechanical properties.Under the condition of solution treatment(T_S=560 ?,t_S=120 min)on AA6061,the elongation increases by 300%,the strength and the hardness decrease dramatically.The AA6061 tube meets the requirement of internal high pressure forming by the improving of formability.The aging treatment of AA6061 is analyzed.Under the condition of aging treatment(T_A=180 ?,t_A=360 min)on AA6061,the plasticity decreases,the strength and the hardness recover to the original condition which ensure formed parts have the mechanical properties of base metal.The technological process of solution treatment — granule medium internal high pressure forming — aging treatment is applied to manufacture the typical pipe fittings of convex ring tube in free bulging,stepped shaft tube and tubes with hexagonal and square section.The theoretical forming limit diagram(FLD)is also applied to analyze and predict the fracture trend of forming tube.The studies show that,the maximum expansion ratio of AA6061 extruded tube increase by 25% by this process.The material properties of formed fittings reach the performance index of raw material.Therefore,the forming of AA6061 tube at room temperature is realised by this technology.