Formability and strengthening mechanism of AA6061 tubular components under solid granule medium internal high pressure forming
(1. Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education, Yanshan University, Qinhuangdao 066004, China;
2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;
3. Qinhuangdao North Metal Hose Co., Ltd., Qinhuangdao 066004, China;
4. School of Vehicles and Energy, Yanshan University, Qinhuangdao 066004, China)
Abstract: A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube can be adjusted by heat treatment to satisfy the process requirements and the processing method can also be realized by granule medium internal high pressure forming technology with the features of convenient implementation, low requirement to equipment and flexible design in product. Results show that, at a solution temperature of 560 °C and time of 120 min, the elongation of AA6061 increases by 313%, but the strength and the hardness dramatically decrease. At an aging temperature of 180 °C and time of 360 min, the strength and hardness of AA6061 alloy are recovered to the values of the as-received alloy. The maximum expansion ratio (MER) of AA6061 tube increases by 25.5% and the material properties of formed tube reach the performances of raw material.
Key words: AA6061 alloy; internal high pressure forming; heat treatment; strengthening mechanism