Enhancing energy absorption performance in additively manufactured lattice structures: A synergistic approach to geometry and alloy design

• A combined geometry and alloy approach was used to design steel lattice structures. • Steels were designed to activate transformation- or twinning-induced plasticity. • An f2ccz structure was selected and modified to benefit from plasticity effects. • Leveraging plasticity effects significantly enhanced energy absorption performance. The design flexibility offered by powder bed fusion using a laser beam enables the production of parts with complex geometries, such as topologically ordered, strut-based lattice structures. Research on lattice structures has predominantly focused on tailoring the macroscopic mechanical response through geometrical design rather than material characteristics. This study, on the other hand, aims for a synergistic approach focusing on both geometry and alloy design to enhance the energy absorption performance of high-manganese steel (HMnS) lattice structures. In HMnS, different deformation mechanisms, such as transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), can be activated in addition to dislocation slip, depending on the stacking fault energy of the alloy. When effectively activated, these mechanisms, particularly TRIP, lead to pronounced strain hardening that contributes to the energy-absorption capacity of a lattice structure. For this purpose, an f2ccz lattice structure was selected as the reference design, and the unit cell geometry was modified to effectively leverage TRIP and/or TWIP effects. Thereby, the mechanical stability was significantly improved, and the energy-absorption capacity was increased by 22 %. Furthermore, the findings highlight the potential for extending the alloy-geometry synergy to chemically or functionally graded structures, enabling precise control over local behaviour and enhancing global performance.