Superplastic-like forming of non-superplastic AA5083 combined with mechanical pre-forming

Abstract

Superplastic forming has been considered as an attractive process in the automotive and aerospace industries. However, the disadvantages of slow forming rate, high-temperature requirement, poor thickness distribution, and expensive base material have hindered its widespread use for high production volume. In this paper, the non-superplastic grade of 5083 aluminum alloy (AA5083) sheets with thickness of 3 mm was employed in a superplastic-like forming process, which is a combination of drawing (mechanical pre-forming) and superplastic forming (blow forming). Experimental trials were conducted to verify the possibility of improving the forming rate and lowering the process temperature. The blank was firstly pre-formed during the mechanical pre-forming phase. As a result, some part of material along the flange area was introduced inside the deformation cavity in advance of the blow forming phase. Secondly, argon gas was applied on the sheet, which would be deformed to come into contact with the inner die surface at the end of pressure cycle. It took only 8 min for the blow forming phase, and the process achieved an almost fully formed part at 400°C. The minimum thickness occurred at the inward corners, and the maximum thinning of the formed part was 54%. Grain growth and cavitation were found from the microstructure observations.