Mechanical metamaterials with three-dimensional micro- and nanoarchitectures exhibit unique mechanical properties, such as high specific modulus, specific strength, and energy absorption. However, a conflict exists between strength and recoverability in nearly all the mechanical metamaterials reported recently, in particular the architected micro/nanolattices, which restricts the applications of these materials in energy storage/absorption and mechanical actuation. Here, we demonstrated the fabrication of three-dimensional architected composite nanolattices that overcome the strength-recoverability trade-off. The nanolattices under study are made up of a high-entropy alloy-coated (14.2-126.1 nm in thickness) polymer strut (approximately 260 nm in the characteristic size) fabricated via two-photon lithography and magnetron sputtering deposition. In situ uniaxial compression inside a scanning electron microscope showed that these composite nanolattices exhibit a high specific strength of 0.027 MPa/kg m, an ultrahigh energy absorption per unit volume of 4.0 MJ/m, and nearly complete recovery after compression under strains exceeding 50%, thus overcoming the traditional strength-recoverability trade-off. During multiple compression cycles, the composite nanolattices exhibit a high energy loss coefficient (converged value after multiple cycles) of 0.5-0.6 at a compressive strain beyond 50%, surpassing the coefficients of all the micro/nanolattices fabricated recently. Our experiments also revealed that, for a given unit cell size, the composite nanolattices coated with a high entropy alloy with thickness in the range of 14-50 nm have the optimal specific modulus, specific strength, and energy absorption per unit volume, which is related to a transition of the dominant deformation mechanism from local buckling to brittle fracture of the struts.

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The authors report a simple Fe-based Fe71Nb6B23 ternary bulk metallic glass with a record high strength of 4.85GPa as well as an appreciable compressive plastic strain of 1.6%. This finding is associated with the unique attribute of the alloying element Nb, which favors the formation of a networklike structure and holds high Poisson’s ratio. A fracture feature with a combination of vein pattern and nanoscale corrugations under compression is clearly characterized in this glass. The fractographic observations correlate well with the observed improvements in plasticity.

Deformation of ductile crystalline-amorphous nanolaminates is not well understood due to the complex interplay of interface mechanics, shear banding, and deformation-driven chemical mixing. Here we present indentation experiments on 10 nm nanocrystalline Cu-100 nm amorphous CuZr model multilayers to study these mechanisms down to the atomic scale. By using correlative atom probe tomography and transmission electron microscopy we find that crystallographic slip bands in the Cu layers coincide with noncrystallographic shear bands in the amorphous CuZr layers. Dislocations from the crystalline layers drag Cu atoms across the interface into the CuZr layers. Also, crystalline Cu blocks are sheared into the CuZr layers. In these sheared and thus Cu enriched zones the initially amorphous CuZr layer is rendered into an amorphous plus crystalline nanocomposite.

We report high strength reliability under tension of a bulk metallic glass (BMG), demonstrated by its high uniformity in strength found over a statistically significant number of specimens, despite the fact that the samples all showed no macroscopic plasticity. Weibull statistical analysis showed that the Weibull modulus of the material is 36.5, which is much higher than the values of more typical brittle materials, further confirming BMGs’ high reliability [Appl. Mech. Rev. 5, 449 (1952)].

During joint inflammation, various reactive oxygen species (ROS) are present in the surrounding tissue and joint fluid. In the laboratory, hydrogen peroxide (H 2 O 2) is typically used to simulate inflammatory conditions, and media containing proteins and hyaluronic acid (HA) are employed to simulate joint synovial fluid. Electrochemical interactions between H 2 O 2 and HA in the presence of a CoCrMo surface are expected, since HA molecules contain redox-active moieties. We hypothesized that any redox reactions of these moieties with ROS will mitigate the oxidizing effect of H 2 O 2 on the CoCrMo surface, limiting the corrosion rate of the metal. Non-destructive electrochemical measurements (open circuit potential, linear polarization resistance and electrochemical impedance spectroscopy) were used to investigate the corrosion response of CoCrMo in synovial model fluid containing physiologically relevant concentrations of albumin proteins and hyaluronic acid, with and without H 2 O 2. Two different molarities of H 2 O 2 , 3 mM and 30 mM, were tested. While both molarities are within physiological limits, 3mM is well within the range HA could mitigate, whereas 30 mM is not. Contrary to our hypothesis, HA did not alleviate corrosion in 3 mM H 2 O 2 and even caused a corrosion increase in the case of 30 mM H 2 O 2. The decrease in corrosion resistance of the alloy may be attributed to the complexation of degenerated HA molecular chains with chromium ions released from the metallic surface, which are necessary to build a protective oxide film. This finding has clinical implications, suggesting that HA accelerates corrosion of CoCrMo implants in the presence of strong inflammation.