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Materials that exhibit yielding behavior are used in many applications, from spreadable foods and cosmetics to direct write three-dimensional printing inks and filled rubbers. Their key design feature is the ability to transition behaviorally from solid to fluid under sufficient load or deformation. Despite its widespread applications, little is known about the dynamics of yielding in real processes, as the nonequilibrium nature of the transition impedes understanding. We demonstrate an iteratively punctuated rheological protocol that combines strain-controlled oscillatory shear with stress-controlled recovery tests. This technique provides an experimental decomposition of recoverable and unrecoverable strains, allowing for solid-like and fluid-like contributions to a yield stress material’s behavior to be separated in a time-resolved manner. Using this protocol, we investigate the overshoot in loss modulus seen in materials that yield. We show that this phenomenon is caused by the transition from primarily solid-like, viscoelastic dissipation in the linear regime to primarily fluid-like, plastic flow at larger amplitudes. We compare and contrast this with a viscoelastic liquidwith no yielding behavior, where the contribution to energy dissipation from viscous flow dominates over the entire range of amplitudes tested.

Mechanical metamaterials with high recoverable elastic energy density, which we refer to as high-enthalpy elastic metamaterials, can offer many enhanced properties, including efficient mechanical energy storage 1 , 2 , load-bearing capability, impact resistance and motion agility. These qualities make them ideal for lightweight, miniaturized and multi-functional structures 3 , 4 , 5 , 6 , 7 – 8 . However, achieving high enthalpy is challenging, as it requires combining conflicting properties: high stiffness, high strength and large recoverable strain 9 , 10 – 11 . Here, to address this challenge, we construct high-enthalpy elastic metamaterials from freely rotatable chiral metacells. Compared with existing non-chiral lattices, the non-optimized chiral metamaterials simultaneously maintain high stiffness, sustain larger recoverable strain, offer a wider buckling plateau, improve the buckling strength by 5–10 times, enhance enthalpy by 2–160 times and increase energy per mass by 2–32 times. These improvements arise from torsional buckling deformation that is triggered by chirality and is absent in conventional metamaterials. This deformation mode stores considerable additional energy while having a minimal impact on peak stresses that define material failure. Our findings identify a mechanism and provide insight into the design of metamaterials and structures with high mechanical energy storage capacity, a fundamental and general problem of broad engineering interest. High-enthalpy elastic metamaterials constructed from freely rotatable chiral metacells have high stiffness, large recoverable strain and improved buckling strength.

Carbon aerogels are elastic, mechanically robust and fatigue resistant and are known for their promising applications in the fields of soft robotics, pressure sensors etc. However, these aerogels are generally fragile and/or easily deformable, which limits their applications. Here, we report a synthesis strategy for fabricating highly compressible and fatigue-resistant aerogels by assembling interconnected carbon tubes. The carbon tube aerogels demonstrate near-zero Poisson’s ratio, exhibit a maximum strength over 20 MPa and a completely recoverable strain up to 99%. They show high fatigue resistance (less than 1.5% permanent degradation after 1000 cycles at 99% strain) and are thermally stable up to 2500 °C in an Ar atmosphere. Additionally, they possess tunable conductivity and electromagnetic shielding. The combined mechanical and multi-functional properties offer an attractive material for the use in harsh environments. Carbon aerogels are generally fragile and tend to collapse under large compressive strain. Here, the authors demonstrate that the mechanical strength, elasticity, and fatigue resistance can be improved by fabricating aerogels with interconnected carbon tubes.

Many established, but also potential future applications of NiTi-based shape memory alloys (SMA) in biomedical devices and solid-state refrigeration require long fatigue life with 10 7 –10 9 duty cycles 1 , 2 . However, improving the fatigue resistance of NiTi often compromises other mechanical and functional properties 3 , 4 . Existing efforts to improve the fatigue resistance of SMA include composition control for coherent phase boundaries 5 – 7 and microstructure control such as precipitation 8 , 9 and grain-size reduction 3 , 4 . Here, we extend the strategy to the nanoscale and improve fatigue resistance of NiTi via a hybrid heterogenous nanostructure. We produced a superelastic NiTi nanocomposite with crystalline and amorphous phases via severe plastic deformation and low-temperature annealing. The as-produced nanocomposite possesses a recoverable strain of 4.3% and a yield strength of 2.3 GPa. In cyclic compression experiments, the nanostructured NiTi micropillars endure over 10 8 reversible-phase-transition cycles under a stress of 1.8 GPa. We attribute the enhanced properties to the mutual strengthening of nanosized amorphous and crystalline phases where the amorphous phase suppresses dislocation slip in the crystalline phase while the crystalline phase hinders shear band propagation in the amorphous phase. The synergy of the properties of crystalline and amorphous phases at the nanoscale could be an effective method to improve fatigue resistance and strength of SMA. Increasing the fatigue life of shape memory alloys often compromises other mechanical properties such as yield strength and plastic deformation behaviour. Introducing a mixed nanostructure of crystalline and amorphous phases can enable superelasticity in NiTi micropillars with recoverable strain of 4.3%, yield strength of 2.3 GPa and 10 8 reversible-phase transition cycles under a stress of 1.8 GPa.

In advanced applications such as aerospace and space exploration, materials must balance lightness, functionality and extreme thermal fluctuation resistance 1 , 2 . Shape-memory alloys show promise with strength, toughness and substantial strain recovery due to superelasticity, but maintaining low mass and effective operation at cryogenic temperatures is challenging 3 , 4 , 5 – 6 . We hereby introduce a new shape-memory alloy that adheres to these stringent criteria. Predominantly composed of Ti and Al with a chemical composition of Ti 75.25 Al 20 Cr 4.75 , this alloy is characterized by a low density (4.36 × 10 3  kg m − 3 ) and a high specific strength (185 × 10 3  Pa m 3 per kg) at room temperature, while showing excellent superelasticity. The superelasticity, owing to a reversible stress-induced phase transformation from an ordered body-centred cubic parent phase to an ordered orthorhombic martensite, allows for a recoverable strain exceeding 7%. This functionality persists across a broad range of temperatures, from deep cryogenic 4.2 K to above room temperature, arising from an unconventional temperature dependence of transformation stresses. Below a certain threshold during cooling, the critical transformation stress inversely correlates with temperature. We interpret this behaviour from the perspective of a temperature-dependent anomalous lattice instability of the parent phase. This alloy holds potential in everyday appliances requiring flexible strain accommodation, as well as components designed for extreme environmental conditions such as deep space and liquefied gases. A Ti–Al-based shape-memory alloy adhering to the stringent criteria of lightness, functionality and extreme thermal fluctuation resistance is introduced, showing excellent superelasticity with a recoverable strain exceeding 7% and an ultra-wide temperature window from 4.2 K to 400 K.

The printability, microstructural characteristics, phase transformation behaviors, and mechanical properties of LPBF-fabricated NiTi alloys are reviewed. Several common structures for LPBF-fabricated NiTi alloys are considered and their various fields of application are illustrated. The technical challenges, limitations, and development tendencies of LPBF-fabricated NiTi alloys are put forward. NiTi alloys have drawn significant attentions in biomedical and aerospace fields due to their unique shape memory effect (SME), superelasticity (SE), damping characteristics, high corrosion resistance, and good biocompatibility. Because of the unsatisfying processabilities and manufacturing requirements of complex NiTi components, additive manufacturing technology, especially laser powder bed fusion (LPBF), is appropriate for fabricating NiTi products. This paper comprehensively summarizes recent research on the NiTi alloys fabricated by LPBF, including printability, microstructural characteristics, phase transformation behaviors, lattice structures, and applications. Process parameters and microstructural features mainly influence the printability of LPBF-processed NiTi alloys. The phase transformation behaviors between austenite and martensite phases, phase transformation temperatures, and an overview of the influencing factors are summarized in this paper. This paper provides a comprehensive review of the mechanical properties with unique strain-stress responses, which comprise tensile mechanical properties, thermomechanical properties (e.g. critical stress to induce martensitic transformation, thermo-recoverable strain, and SE strain), damping properties and hardness. Moreover, several common structures (e.g. a negative Poisson’s ratio structure and a diamond-like structure) are considered, and the corresponding studies are summarized. It illustrates the various fields of application, including biological scaffolds, shock absorbers, and driving devices. In the end, the paper concludes with the main achievements from the recent studies and puts forward the limitations and development tendencies in the future.

HighlightsThe large-sheet holey graphene framework/SiO (LHGF/SiO) composite displays notably high recoverable strain, suggesting considerably improved mechanical flexibility and robustnessThe LHGF/SiO anode with a mass loading of 44 mg cm−2 delivers a high areal capacity of 35.4 mAh cm−2 at current density of 8.8 mA cm−2 and retains a capacity of 10.6 mAh cm−2 at 17.6 mA cm−2The LHGF/SiO anode with an ultra-high mass loading of 94 mg cm−2 delivers an extraordinary areal capacity up to 140.8 mAh cm−2, about 1–2 order of magnitude higher than those in typical commercial devicesSilicon monoxide (SiO) is an attractive anode material for next-generation lithium-ion batteries for its ultra-high theoretical capacity of 2680 mAh g−1. The studies to date have been limited to electrodes with a relatively low mass loading (< 3.5 mg cm−2), which has seriously restricted the areal capacity and its potential in practical devices. Maximizing areal capacity with such high-capacity materials is critical for capitalizing their potential in practical technologies. Herein, we report a monolithic three-dimensional (3D) large-sheet holey graphene framework/SiO (LHGF/SiO) composite for high-mass-loading electrode. By specifically using large-sheet holey graphene building blocks, we construct LHGF with super-elasticity and exceptional mechanical robustness, which is essential for accommodating the large volume change of SiO and ensuring the structure integrity even at ultrahigh mass loading. Additionally, the 3D porous graphene network structure in LHGF ensures excellent electron and ion transport. By systematically tailoring microstructure design, we show the LHGF/SiO anode with a mass loading of 44 mg cm−2 delivers a high areal capacity of 35.4 mAh cm−2 at a current of 8.8 mA cm−2 and retains a capacity of 10.6 mAh cm−2 at 17.6 mA cm−2, greatly exceeding those of the state-of-the-art commercial or research devices. Furthermore, we show an LHGF/SiO anode with an ultra-high mass loading of 94 mg cm−2 delivers an unprecedented areal capacity up to 140.8 mAh cm−2. The achievement of such high areal capacities marks a critical step toward realizing the full potential of high-capacity alloy-type electrode materials in practical lithium-ion batteries.

HighlightsThe study reveals the great potential of metal–organic framework (MOF)-based nanocomposites in thermal insulation and fire retardancy applications.A nanoengineering approach was developed to process MOFs into freestanding, mechanically strong, and elastic aerogels, which may boost the fundamental research and practical applications of MOFs in these areas.

The shape recovery ability of shape-memory alloys vanishes below a critical size (~50 nm), which prevents their practical applications at the nanoscale. In contrast, ferroic materials, even when scaled down to dimensions of a few nanometers, exhibit actuation strain through domain switching, though the generated strain is modest (~1%). Here, we develop freestanding twisted architectures of nanoscale ferroic oxides showing shape-memory effect with a giant recoverable strain (>8%). The twisted geometrical design amplifies the strain generated during ferroelectric domain switching, which cannot be achieved in bulk ceramics or substrate-bonded thin films. The twisted ferroic nanocomposites allow us to overcome the size limitations in traditional shape-memory alloys and open new avenues in engineering large-stroke shape-memory materials for small-scale actuating devices such as nanorobots and artificial muscle fibrils. Shape-memory materials are promising actuation sources for small-scale machines. The authors demonstrate that domain switching in twisted ferroic nanocomposites enables a giant shape-memory effect and superelasticity in the nanoscale structure.

Superelasticity – exhibiting either Hookean (linear) or non-Hookean (nonlinear) recoverable strain beyond 2% – has been realized in distinct material systems such as metallic glasses, shape memory alloys, strain glass alloys and Gum metals, enabling diverse technological applications. Here we demonstrate that, through compositional tuning in a high-entropy alloy, the elastic behavior can be continuously and reversibly modulated between Hookean superelasticity, non-Hookean superelasticity with an ultrahigh recoverable strain of ~8%, and back to the Hookean regime. By combining atomic-scale strain mapping and extensive first-principles calculations, we reveal that this tunability is governed by a hidden strain order, arising from frustrated crystallization of two competing phases. As a result, local lattice distortion arises, producing a heterogeneous strain landscape that modulates phase stability, phase transformation propensity, and elastic response. Our findings establish a materials design strategy for programming Hookean and non-Hookean elasticity behavior on demand, with promising applications in microelectromechanical systems, high-precision actuators, and adaptive damping devices. Designing superelastic materials remains challenging. Here, the authors reveal that hidden atomic-scale strain order in a high-entropy alloy enables reversible switching between linear and nonlinear superelasticity through subtle composition tuning.