Spinning process of 2219 aluminum alloy tubes for used in hydroforming

2219 aluminum alloy thin-walled tubes were fabricated by multi-pass spinning process, and then heat treatments were employed to optimize the mechanical properties of the spun tubes. It is shown that severe deformation during the spinning leads to the formation of large number of nanoscale subgrains, which causes the decrease of work hardening rate, ultimate tensile strength, and fracture strain. The solid solution at 530℃/30 min results in the full recrystallization and leads to the disappearance of the nanoscale subgrains. Besides, the micron scale precipitates in the as-spun tubes are refined to be nanoscale via the further aging process conducted at 175℃/18 h. It is why the ultimate strength of the tubes is enhanced from 245 to 435 MPa. By using of the spun tubes, 2219 aluminum alloy bellows with four circumferential waves were successfully formed by multi-step single wave hydroforming process.