Comparison of Advanced SPF Die Technologies in the Forming of a Production Panel

Superplastic forming (SPF) is a manufacturing process that can facilitate increased use of aluminum in automobile body structures. Despite considerable advantages with regards to formability and tooling costs, the process has been mostly limited to low volume production due to relatively long cycle times and the need to use specially processed sheet alloys. To address these issues, advanced processes such as two stage gas forming (TSGF) and hot draw mechanical pre-forming (HDMP) have been developed. Advantages of these processes have been demonstrated on the forming of a complex dash panel part. Final thickness distribution and forming time on this part manufactured with these two processes were compared to that of the same panel produced with conventional SPF. The HDMP technology which combines hot stamping with SPF was found to have the capability of forming a complex shaped component with a superior thickness profile and faster forming cycle than that formed with a conventional single stage or two stage forming cycle. Additionally, the HDMP process proved to be a robust process with a wide temperature window and allowed for the forming of lower-cost, non-spf aluminum, and magnesium sheet alloys. Finally, analysis of the post-form microstructure indicated that there was essentially no cavitation in panels formed with the HDMP process and that material with a coarse grain structure could be successfully formed.