Reusable energy-absorbing NiTi alloy assembled mechanical metamaterials with ultra-large recoverable strain and ultra-high cyclic stability

• NiTi-AMM achieves 96.7 % shape recovery rate under 85 % compressive strain . • NiTi-AMM maintains 82.7 % shape recovery rate after 10,000 compression cycles. • Cumulative volume-specific energy absorption of NiTi-AMM reaches 230.9 MJ/m³. • Superelastic NiTi alloy and AMM configuration enhance deformation capacity. • NiTi-AMM demonstrates high cyclic stability and reusability . Reusable energy-absorbing metal structures are essential for safeguarding vital components against repetitive collisions and impacts. However, conventional energy-absorbing metal structures cannot revert to their original shape post-impact, thereby restricting their reusability. This study presents a novel approach that integrates a superelastic nickel-titanium alloy with reversible stress-induced martensitic transformation and an assembled mechanical metamaterial (AMM) configuration to create a reusable energy-absorbing nickel-titanium AMM (NiTi-AMM) featuring exceptional deformation capacity and cyclic stability. The NiTi-AMM demonstrates a shape recovery rate (R rec ) of 96.7 % under 85 % compressive strain. After 10,000 cycles at 85 % compressive strain, the R rec remains at 82.7 %, indicating outstanding cyclic stability. Throughout 10,000 cycles, the cumulative volume-specific energy absorption of NiTi-AMM increases linearly, reaching 230.9 MJ/m³, which represents the highest reported value for reusable energy-absorbing metal structures. This research provides significant insights into advancing high-performance reusable energy-absorbing metal structures.