Exceptional compressive performance in additively manufactured CoCrNi-based hybrid metamaterials enabled by sequential yielding and gradual strain release

Metamaterials are promising candidates for advanced structural applications owing to their exceptional strength-to-weight ratio, energy absorption, and fatigue performance. Realizing these potentials simultaneously requires moving beyond monothetic topology design and developing novel strategies to integrate contradictory mechanical behaviors within components. Here, the design freedom of additive manufacturing is leveraged to break this long-standing performance paradigm via embedding precipitation-hardened inner fillings into a ductile matrix, constructing hybrid metamaterials with high resistance to compressive damage and cyclic fatigue. This design enables a novel strain-dependent, sequential yielding deformation in which soft outer layers dissipate energy during initial compression, followed by progressive engagement of the inner fillings. An observed dual-plateau compressive response synergistically enhances plateau stress and energy absorption. Under cyclic loading, thermally stable cellular structures containing coherent γ′ precipitates alter damage progression and suppress cyclic ratcheting. The acquisition of four-stage fatigue behavior, featuring a stage of gradual strain release, extends fatigue life by over 100%. The synergetic effect of nanoscale precipitation, microscale substructures, and a macroscopic compositional gradient enables strain redistribution and redirects damage to high-tolerance regions. This design presents a novel methodology for fabricating hybrid metamaterials with incompatible mechanical properties, yielding fatigue-resistant structures with enhanced compressive energy absorption for aerospace, automotive, and biomedical applications.