Integrated forming process of selective laser melting near-net-shaped preforms and hot gas bulging for complex-shaped AlSi10Mg alloy parts

Abstract

To overcome the challenges associated with additive manufacturing of large-size, low-stiffness metal thin shells, specifically the difficulty in maintaining dimensional accuracy and the simultaneous occurrence of wrinkling, cracking, and thinning during fluid pressure forming, an integrated forming process of selective laser melting near-net-shaped preform and hot gas bulging was proposed. This study systematically examined the hot formability and the pre-deformed microstructure and properties of selective laser melted AlSi10Mg alloy to determine the optimal process parameters and assess the viability of the proposed integrated forming process for fabricating complex thin-walled parts. Results show that: (1) The selective laser melted AlSi10Mg alloy preforms exhibit excellent microstructural characteristics and superior hot formability, and the feasibility of forming these preforms via hot gas bulging technique was successfully validated. (2) During hot gas bulging process, the precipitation and coarsening of the Si phase, coupled with enhanced dynamic recrystallization, as well as the formation of a uniform dislocation network and deformed twinned Si phase, synergistically contribute to a significant improvement of ductility in the formed parts. (3) Compared to the direct selective laser melting technique, the integrated forming process markedly improved the dimensional accuracy and density of the fabricated parts. The dimensional deviation was reduced from 1.62 mm to below 0.28 mm, while porosity decreased from 0.36 % to 0.07 %. Despite a reduction in tensile strength, the ductility at 25 ℃ and 230 ℃ increased to 18.5 % and 32.5 %, respectively, thereby making the material highly suitable for applications requiring enhanced ductility. The feasibility of selective laser melted preforms via the hot gas bulging process was systematically confirmed, thereby establishing a foundational basis for the prospective application of this integrated forming methodology. The methodologies and insights obtained from this study hold particular significance for the fabrication of large, complex thin-walled metal components, especially in the context of demanding aerospace applications and emerging next-generation transportation systems.