Shengcheng Mao

The rational design of metallic materials with simultaneous ultrahigh strength and high ductility remains a fundamental challenge, as conventional strengthening strategies often exacerbate plastic instability. Here, we reveal that this trade-off can be overcome in a single-phase tri-modal heterostructured CoCrNi multi-principal element alloy with a high fraction of deformed grains by modulating grain heterogeneity. Synthesized via precisely controlled sub-critical annealing, this structure, comprising deformed grains (DGs, ∼22.5%), fine grains (FGs, ∼22.5%), and ultrafine grains (UFGs, ∼55.0%), delivers exceptional yield strength of 1.35 GPa and elongation of 33.4%. This synergistic effect originates from the sequential activation of strengthening mechanisms: initially triggered by the formation of deformation twins (DTs) and Lomer–Cottrell locks within the FGs at 5% strain, followed by the generation of DTs within the UFGs at 20% strain. Such a sequentially activated process promotes sustained hetero-deformation induced stress within the tri-modal heterostructure, providing the essential strain-hardening increment and thereby effectively circumventing the premature saturation typical of bi-modal heterostructures. This unique structural design satisfies the requirements for prolonged strain hardening at ultrahigh stress levels, offering a viable paradigm for exploiting hierarchical heterogeneity to activate staged deformation sequences in high-performance structural alloys.

Lightweight superelastic alloys with temperature-insensitive properties are critical for deep-space exploration devices, yet their development is hindered by the challenge of simultaneously balancing strength, recoverable strain, and temperature sensitivity. Here, we overcome these limitations in a Ti_50.5Zr₄₀Nb₆Sn₂O_1.5 alloy through Zr/O co-doping to induce local chemical orders (LCOs). This strategy yields an unprecedented combination of large recovery strain (ε_r > 4.5%), high superelastic stress (σ_c > 700 MPa), nearly temperature-independent strength (dσ_c/dT ≈ 0.59 MPa·K⁻¹), and stable elastic modulus over a wide temperature range from 123 K to 298 K. These properties arise from the elastic confinement imposed on the transformable matrix induced by the LCOs, which enhances resistance to dislocation slip and suppresses martensitic transformation, while the modulus hardening caused by LCOs due to anharmonic atomic vibrations compensates for matrix softening. This work provides a feasible and effective route for developing high-performance superelastic alloys with wide-temperature stability through LCO engineering.

Manganese-based hybrid metal halides are attractive for scintillator applications due to their high emission efficiency and good stability. However, most high-performance manganese scintillators rely on bulky and complex organic cations as A-site components, which reduce the lattice density and compromise X-ray absorption. To address this issue, we employed a small piperidinium cation (C₅H₁₂N⁺) to synthesize a zero-dimensional manganese halide, (C₅H₁₂N)₂MnBr₄, via solvent evaporation. This material shows green Mn²⁺ emission but suffers from concentration quenching, giving a low PLQY of 23.86%. Through Cd²⁺ alloying, the optimized (C₅H₁₂N)₂MnBr₄: 20%Cd achieves a markedly enhanced PLQY of 78.54%. As a scintillator, it exhibits excellent X-ray absorption─among the highest reported for hybrid manganese scintillators─and a high light yield of 21086 photons/MeV. This improvement results from the synergy between the small A-site cation (providing a compact lattice for strong absorption) and Cd²⁺ alloying (suppressing concentration quenching). A 10 × 10 cm flexible film fabricated by incorporating the alloyed powder into a TPU matrix shows outstanding radiation stability and a high X-ray imaging resolution of 14 lp mm^-1. The combination of strong X-ray absorption, enhanced luminescence, and solution processability opens new opportunities for low-cost, large-area, flexible X-ray detectors and imaging.

Quantum conductance effects start to appear as the size of electronic devices decreases and they are used in the next generation memristors and quantum calculations. Understanding the relationship between line width and resistance is crucial for developing quantized electronic devices. This Letter reports the development of an electromechanical testing device based on microelectromechanical systems integrated within a transmission electron microscope for investigations at atomic resolution. The resistance changes of single crystalline gold (Au) wires, spanning from hundreds of nanometers down to several atoms are investigated. A transition in resistance from quasiballistic to ballistic transport states is uncovered. The experimental data fitted by calculation show that the ballistic transport limit for single crystal Au at room temperature is about 2.5 nm, beyond which the transmission probability experienced a rapid drop.