Optimization of Geometry and Process Parameters in Multi-Directional Forging (MDF)

Multi-Directional Forging (MDF) is one of the promising Severe Plastic Deformation (SPD) method for producing bulk ultrafine-grained alloys However, its industrial application remains limited, mainly because the mechanical gains achieved are often insufficient relative to the energy and load required.This study aims to address this limitation by quantifying and optimizing the effects of three key processing parameters of MDF: initial workpiece geometry, deformation temperature and, single-pass reduction ratio.The initial workpiece geometry parameter was selected as (a, a, a), (a, a, 2a), and (a, a, 4a).And, the deformation temperatures were set at 20 C, 100 C, and 200 C to represent cold, warm, and lowhot forging conditions.Besides, single-pass height reductions of 5%, 10%, and 20% were also chosen.When combined with the variations in billet geometry and forming temperature, the selected parameters constitute a 3 full-factorial design, which would normally require 27 simulations.However, by employing the Taguchi design of experiments (DOE) method, the number of required simulations was effectively reduced to just 9.All parameters not included in the FEA matrix were kept constant across simulations.For each processing scenario, the effective strain and pressing load were recorded.Effective strain was chosen because it correlates directly with mechanical improvements in the material, while pressing load reflects the ease of the forging process.To identify the optimal parameter set, a Taguchi optimization approach was applied.This method, which uses orthogonal arrays to efficiently explore multiparameter design spaces, aimed to maximize the effective strain while minimizing the pressing load.The resulting combination represents the most favorable trade-off between strain enhancement and load reduction.This study demonstrates that the MDF process, when optimized using a Taguchi design, can achieve an effective strain value of 1.566 mm/mm under the optimal parameter combination of 101010 mm billet size, 200 C forming temperature, and 20% height reduction.These results indicate that substantial plastic deformation can be obtained with relatively low forming complexity and thermal input.While the strain levels remain slightly below those of conventional SPD methods like ECAP, the process benefits from lower energy demands and simplified die setups.The findings highlight MDF's potential as a practical and scalable SPD alternative for high-performance aluminum alloys, offering a data-supported route toward energy-efficient bulk nanostructuring and forging process design.