Optimization of Two-Stage Hybrid Forming Process via Quantitative Assessment of Mechanical Properties in AA5052

Abstract

Superplastic forming (SPF) is a promising approach used for manufacturing parts with complex geometries, especially in the automotive, aerospace, and marine industries. However, the wider use of this method is limited by issues of low forming rate, high-temperature requirement, non-uniform thickness distribution, and expensive base materials. The two-stage hybrid forming (HF) method, in which hot-punch forming is executed before the SPF, was introduced to overcome these limitations. In this study, a conventional non-superplastic grade 5052 aluminum (AA5052) alloy with an average grain size of 70 µm was used to evaluate the applicability of two-stage HF for manufacturing parts with complex geometries from coarse grain alloys. Before implementing the two-stage HF, the optimal experimental conditions for hot drawing and hot blowing were first determined. The optimum HF conditions were identified, as follows: a hot-punching temperature of 400oC, punch depth of 35 mm, punching speed of 150 mm/min, blow forming temperature of 500oC, and gas pressure of 2.5 MPa. The HF results were also verified using the finite element method. The finite element analyses results for thickness distribution and optimal process condition were compared with the experimental results for one-stage and two-stage forming, and showed acceptable similarity.