• Ultralight NiTi Gyroid lattices with volume fractions down to 1% were fabricated by LPBF • A high-power–high-scan-speed process window enabled stable ultralight lattice fabrication • Near-complete superelastic and shape memory recoverability was achieved in the ultralight regime • A volume-fraction-governed fracture-mode transition and a semi-empirical criterion were established NiTi shape memory alloys with lattice metamaterials architectures offer a promising route toward lightweight structures capable of reliable and recoverable deformation; however, the functional behavior of such lattice metamaterials in an ultralight regime remains largely unexplored. In this study, ultralight NiTi Gyroid lattice metamaterials with volume fractions ranging from 1% to 4% were designed and fabricated by laser powder bed fusion. By integrating Gyroid-specific design optimization, systematic process window identification, mechanical testing, and finite element analysis, the mechanical behavior, functional response, and deformation modes of these lattices were comprehensively investigated. The results demonstrate that, despite extreme geometric slenderness, ultralight NiTi Gyroid lattices can achieve near- complete functional recoverability, with a superelastic recoverable ratio of up to 93.65% and shape memory recovery exceeding 98.99% at an 8% compressive strain. Moreover, a volume-fraction-governed fracture-mode transition was revealed: ultralight Gyroid lattices exhibit a stable layer-by-layer collapse behavior, whereas denser Gyroid lattices transition to shear-dominated failure above a critical volume fraction of approximately 14%. Importantly, a mechanics-based semi-empirical criterion was established to quantify this critical volume fraction, enabling predictive design of fracture modes in Gyroid lattices. These findings establish a structure-enabled pathway for achieving stable functional performance and predictable deformation behavior in ultralight NiTi Gyroid lattices, providing design guidance for deformation-controlled lattice metamaterials under stringent weight constraints.
Lin et al. (Wed,) studied this question.