Dislocation strengthening, as one of the methods to simultaneously enhance the room temperature strength and ductility of alloys, does not achieve the desired strengthening and plasticity effect during elevated-temperature deformation. Here, we report a novel strategy to boost the dislocation multiplication and accumulation during deformation at elevated temperatures through dynamic strain aging (DSA). With the introduction of the rare-earth element Ho in Mg-Y-Zn alloy, Ho atoms diffuse toward dislocations during deformation at elevated temperatures, provoking the DSA effect, which increases the dislocation density significantly via the interactions of mobile dislocations and Ho atoms. The resulting alloy achieves a great enhancement of dislocation hardening and obtains the dual benefits of high strength and good ductility simultaneously at high homologous temperatures. The present work provides an effective strategy to enhancing the strength and ductility for elevated-temperature materials.

Piezoceramic is ubiquitously used in high-performance sensors and actuators. Three-dimensional (3D) printing of lead zirconate titanate (PZT) is attractive and highly desired for such device applications, but most of the existing methods are inherently limited to micron resolution, which makes them untenable for fabricating complex 3D architectures with high-definition features. Here, an electrohydrodynamic jet (E-Jet) nanoprinting strategy has been proposed to fabricate PZT 3D structures with the characteristics of flexibility and scalability. Different kinds of 3D PZT true nanostructures (resolution ~40 nm, aspect ratio ~400) were directly fabricated using a 100 μm-sized nozzle. And the PZT nanostructures exhibited well-developed perovskite crystal morphology, large elastic strain (elongation ≈ 13%), and high piezoelectric property (d₃₁ ≈ (236.5 × 10⁻¹²) C·N⁻¹). A bionic PZT air-flow sensor was printed to monitor air-flow detection, demonstrating well sensitivity with ultra-slow air-flow of 0.02 m·s⁻¹. The discovery reveals an efficient pathway to 3D-printing PZT nanostructures for next-generation high-performance piezoelectric devices.

Auxetic mechanical metamaterials are artificially architected materials that possess negative Poisson’s ratio, demonstrating transversal contracting deformation under external vertical compression loading. Their physical properties are mainly determined by spatial topological configurations. Traditionally, classical auxetic mechanical metamaterials exhibit relatively lower mechanical stiffness, compared to classic stretching dominated architectures. Nevertheless, in recent years, several novel auxetic mechanical metamaterials with high stiffness have been designed and proposed for energy absorption, load-bearing, and thermal-mechanical coupling applications. In this paper, mechanical design methods for designing auxetic structures with soft and stiff mechanical behavior are summarized and classified. For soft auxetic mechanical metamaterials, classic methods, such as using soft basic material, hierarchical design, tensile braided design, and curved ribs, are proposed. In comparison, for stiff auxetic mechanical metamaterials, design schemes, such as hard base material, hierarchical design, composite design, and adding additional load-bearing ribs, are proposed. Multi-functional applications of soft and stiff auxetic mechanical metamaterials are then reviewed. We hope this study could provide some guidelines for designing programmed auxetics with specified mechanical stiffness and deformation abilities according to demand.