Research on AA6061 tubular components prepared by combined technology of heat treatment and internal high pressure forming

The high strength aluminum alloy tube can not be formed into complex parts for its high strength and poor plasticity at room temperature. However, its elongation increases with temperature elevating. Therefore, warm forming technology is becoming the research hotspot in aluminum alloy tube forming. However, the control requirement of exact forming temperature and the demand of accessories with high temperature resistance make process control difficult and processing cost high. Based on this point, this study puts forward a new technological process: solution treatment + granules medium internal high pressure forming + artificial aging. During this process, the tested alloy via solution treatment satisfied the process requirements and the granules medium internal high pressure forming method for high strength aluminum alloy tube was also realized by using convenient implementation with low requirement of equipment and flexible design of product. In this paper, the AA6061 extruded tube is investigated to research the effect of heat treatment on mechanical properties. At a solution temperature of 560 degrees C and time of 120 min, the elongation of the AA6061 extruded tube increases by 258%, the strength and the hardness dramatically decrease too. Therefore, the AA6061 tube meets the requirement of internal high pressure forming because of the improvement of formability. At an aging temperature of 180 degrees C and time of 360 min, the strength and hardness of AA6061 recover to the as-received alloy. The typical part of stepped shaft tube was successfully trial-produced in lab by using the present forming method. The maximum expansion ratio (MER) of the AA6061 extruded tube increases by 25%. The theoretical forming limit diagram (FLD) is also applied to analyze and predict the fracture trend of forming tube. (C) 2016 Published by Elsevier B.V.