Topology-controlled high-strain-rate deformation and energy absorption in LPBF-fabricated Inconel 718 lattice structures
Akhil Kumar D, Veera Siva Reddy B, Aditya Ranjan Gupta, Chandrasekhara Sastry C, Hafeezur Rahman A, Lakshmana Rao CPurpose
Additively manufactured metallic lattice structures are promising candidates for impact-resistant and energy-absorbing applications; however, the role of lattice topology in governing deformation stability and energy absorption (EA) under extreme strain-rate loading remains insufficiently understood, particularly for high-strength nickel-based superalloys. The purpose of this study is to systematically investigate the influence of lattice architecture on the dynamic compression behavior, strain-rate stability and EA performance of laser powder bed fusion (LPBF) fabricated Inconel 718 (IN718) lattice structures under high-velocity impact conditions.
Design/methodology/approach
LPBF-fabricated IN718 lattice structures with three distinct topologies: body-centered cubic with vertical struts (BCCz), Hexstar and Honeycomb were subjected to Split Hopkinson pressure bar (SHPB) testing at impact velocities of 20 and 25 m/s. Dynamic true stress–strain response, strain-rate evolution and EA were correlated with synchronized high-speed deformation imaging. Post-compression multiscale characterization was performed using field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy and energy-dispersive X-ray spectroscopy to elucidate topology-dependent deformation mechanisms, lattice stability and microstructural integrity.
Findings
The dynamic response of IN718 lattices is strongly governed by topology. The BCCz lattice exhibited bending-dominated deformation with pronounced strain localization, unstable strain-rate evolution and moderate EA. The Hexstar lattice showed mixed bending-stretching behavior with higher initial stiffness but underwent layer-wise instability at elevated impact velocity. In contrast, the Honeycomb lattice maintained highly stable strain-rate evolution (>3,000 s−1), sustained load-bearing capacity and exceptionally high EA (87 MJ/m³ at 25 m/s) without catastrophic collapse. Multiscale characterization confirmed retention of the face-centered cubic γ-phase across all topologies, with deformation-induced microstrain and lattice disorder governed by architecture rather than chemistry or phase transformation.
Originality/value
This work establishes a direct, experimentally validated link between lattice topology, strain-rate stability and EA efficiency in LPBF-fabricated IN718 under extreme dynamic loading. The study demonstrates that stretch-dominated Honeycomb architectures provide a topology-driven pathway for achieving simultaneous deformation stability and ultra-high EA in nickel-based superalloy lattices. The findings deliver clear design guidelines for architected impact-resistant and blast-mitigation structures fabricated by additive manufacturing.