Exploring the Influence of Pre/Post-Aging on Springback in Al-Mg-Si Alloy Tube Bending

Abstract Aluminium alloy (Al-alloy) bent tube is one kind of strategic lightweighting components, which attracts application in industrial clusters, such as automobile, aerospace, etc. To meet the demands on high-precision manufacturing, springback gains nowadays increased attention since it causes a series of problems such as increased tolerance limits, variabilities in assembly and service performance. Many Al-alloys exhibit significant naturally aging properties, which is closely related to the control of dimensional accuracy and performance of products. Thus, as one of the most important issues affecting the dimensional accuracy, springback becomes a challenging issue in the precision forming of Al-alloys, and it is of importance to well understand the aging-related springback phenomena. In this research, using rotary draw bending of a typical Al-Mg-Si alloy tube as the case, the influence of natural aging before and after the forming operation on springback is experimentally studied. Firstly, the as-received AA6060-T4 tubes are solution-heat-treated (SHTed) to obtain fully-annealed samples. Then, the tube samples are used for three experimental schemes related to aging and bending. By bending experiments of the samples with pre natural aging (pre-NA) periods from 30 min the 56 days, the influence of pre-NA time on springback is identified. Meanwhile, through bending experiments of the tubes without pre-NA, and followed by measuring the bending angles of the bent samples after different post natural aging (post-NA) time up to 35 days, the time-dependent springback behaviour is studied. Furthermore, through the experimental design of tube bending without pre-NA, and followed by the post artificial aging (post-AA) treatment, the dimension variations of bent tubes during the post-AA process are examined to explore the possible manufacturing approach for tailoring the geometry accuracy and performance of bent parts. Through this work, a fundamental understanding of the influence of pre/post-aging on springback is provided, which can help control the product accuracy of bent Al-alloy tubular products.