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The impact of annealing on the recrystallized grain structure and superplastic behavior of two Al-Mg 5xxx alloys used for high-speed blow forming (HSBF) was studied. The results revealed that both alloys demonstrated rapid static recrystallization after only a few minutes of annealing at 520 °C, forming fine and equiaxed grain structures. After four min of annealing, Alloy 2 (Al-4.0Mg-1.18Mn) exhibited a higher fraction of small grains (<10 µm) compared to Alloy 1 (Al-4.5Mg-0.74Mn). Moreover, Alloy 2 displayed enhanced resistance to grain coarsening with increasing annealing times, which was attributed to its higher amount of Al₆(Mn,Fe) intermetallic particles and a higher number density of Mn dispersoids. Optimizing the annealing time can effectively develop a fine and stable grain structure in Al-Mg 5xxx alloys. During tensile deformation, Alloy 2 consistently showed higher ductility compared to Alloy 1 at low strain rates (170% vs. 138% at 0.001 s⁻¹ and 163% vs. 134% at 0.01 s⁻¹), whereas at a high strain rate of 1 s⁻¹, both alloys displayed comparable tensile elongation. The high superplastic response of Alloy 2 at low strain rates renders it a superior superplastic alloy for HSBF applications. Full article

The auto industry aims to deliver cost-effective, efficient vehicles to meet customer needs. They are utilizing aluminum to lower expenses, enhance durability, and lighten vehicles. Currently, the industry is developing a high-speed blow forming (HSBF) technique—a faster version of the aluminum thermoforming process, superplastic forming (SPF). HSBF allows the rapid creation of aluminum bodywork or structural parts at high temperatures using pressurized gas. It can produce up to 25 parts per hour, significantly faster than SPF, which only produces 4 parts per hour. The primary objective of this project is to select and characterize a seal that can increase the production rate to 120 parts per hour by allowing the sheet to flow into the mold, especially during the initial stages of the forming process, where most of the deformation occurs. Several test benches were developed to assess the performance and durability of the selected high-temperature seals under conditions that imitate the HSBF process. During the tests, low air pressures are applied to a gasket-enclosed cavity and the resulting mass-flow leakage is measured. The temperature of the mold is kept constant at approximately the superplastic temperature of the aluminum alloy. Through testing, we derived leakage mass flow curves based on cycle count, showcasing the superior sealing ability and longevity of packing seals in HSBF conditions. The seals displayed good durability and sealing performance under HSBF operational conditions, sustaining over 3000 cycles. Moreover, the seals attained a leakage mass flow rate of around 0.3 g/s·m·bar, nearly ten times below the target application limit of 2 g/s·m·bar, confirming their superior performance. Full article

High-speed blow forming (HSBF) is a new technology for producing components with complex geometries made of high strength aluminum alloy sheets. HSBF is considered a hybrid-superplastic forming method, which combines crash forming and gas blow forming. Due to its novelty, optimization of the deformation process parameters is essential. In this study, using the finite element (FE) code ABAQUS, thinning of an aluminum component produced by HSBF under different strain rates was investigated. The impact of element size, variation of friction coefficient, and material constitutive model on thinning predictions were determined and quantified. The performance of the FE simulations was validated through forming of industrial size parts with a complex geometry for the three investigated strain rates. The results indicated that the predictions are sensitive to the element size and the coefficient of friction. Remarkably, compared to a conventional power law model, the variable m-value viscoplastic (VmV) model could precisely predict the thickness variation of the industrial size component. Full article