Lei Zhang

Silver‐based materials are extensively employed in sliding electrical contacts; however, their tribological performance is often limited by the intrinsic softness and poor wear resistance of pure silver. Recent advancements in multiphase composite designs, incorporating solid lubricants and reinforcing phases, have facilitated substantial enhancements in wear behavior through the implementation of tailored interface engineering methodologies. This review systematically examines the low‐wear mechanisms in silver‐based multiphase composites, with a focus on the coevolution of material and tribological interfaces under friction. The ensuing discourse will address the collective influence of a ductile silver matrix, lubricative phases, and reinforcing constituents on stress distribution, third‐body formation, and tribofilm development. Subsequently, a thorough analysis of the key friction‐induced structural changes is conducted, encompassing tribo‐oxidation, surface amorphization, and gradient nanocrystallization. This analysis is complemented by an examination of self‐healing processes, which enhance interface stability and reduce wear. Furthermore, this review underscores the advent of ultra‐low‐wear regimes facilitated by self‐lubrication, friction‐induced gradient nanostructures, and synergistic coupling between internal material interfaces and external tribo‐interfaces. A combination of ex situ and in situ/operando characterization techniques, as well as multiscale simulations, is employed to establish design principles that link phase selection, interface architecture, and environmental conditions to friction and wear performance.

To address the oxidation challenges of inert anodes in aluminum electrolysis, a series of novel Fe34.5Ni40.5Cr15Al10-xTix (x = 2, 3, 4) high-entropy alloys were designed by Thermo-Calc software and were fabricated via vacuum arc melting. A systematic investigation was conducted on the influence of the Al/Ti ratio on the high-temperature oxidation resistance of the alloys. A dual-phase microstructure comprising FCC and B2 phases is observed in the as-cast alloy. The alloy demonstrates exceptional oxidation resistance at 960 °C. Oxidation kinetics analysis reveals that its oxidation follows a parabolic rate law, controlled by diffusion. An adequate Al content favors the formation of a dense and stable Al2O3 layer, whereas an appropriate Ti addition alleviates the thermal expansion mismatch between the oxide scale and the substrate. Consequently, the Al7Ti3 composition achieves a very low parabolic rate constant of 0.0895 mg2·cm-4·h-1, which is 98.52% lower than other traditional anode materials like Cu-Ni-Cr alloys. This study delivers a theoretical basis for designing high-entropy alloys applied to inert anodes in aluminum electrolysis.

This study developed a high oxidation resistance cermet via an improved processing route combining powder metallurgy with sintering under controlled oxygen partial pressure. The microstructural evolution, mechanical properties, and high-temperature oxidation behavior were investigated. During sintering, interphase mass exchange occurred where Fe diffused into the spinel lattice, reducing Fe3+ to Fe2+ and substituting for Ni2+ to form Fe3O4, while displaced Ni diffused back into the metallic phase, as confirmed by EPMA and XPS analyses. Optimal mechanical properties were achieved at 1250 ℃and 100 ppm, yielding a relative density of 93.7%, a flexural strength of 167.2 ± 15.1 MPa, and a compressive strength of 636.9 ± 28.5 MPa. Oxidation at 800 °C followed parabolic kinetics, forming a stable, 35.09 μm thick multi-layered scale after 24 h. This protective scale consisted of an outer CuO layer, intermediate CuFe2O4 and NiFe2O4 spinels, and an inner Fe3O4 layer, effectively inhibiting further oxidation. This work demonstrates the potential of the designed cermet as a promising inert anode material.

Friction and wear of metallic materials are ubiquitous in modern life, resulting in significant energy consumption and property damage. The tribological performance of metallic materials is greatly affected by their surface characteristics, motivating the rapid development of surface treatment technology. As a simple method without changing the matrix composition, mechanically induced surface nanocrystallization has emerged as a promising strategy to achieve reduced friction coefficients and increased wear resistance for metals. This review highlights the systemic progress and prospects of mechanically induced surface nanocrystallization, emphasizing its impact on mitigating friction and wear in metals. The review begins by presenting various processing techniques for preparing surface nanostructures, followed by an in-depth discussion on the mechanisms of mechanically induced surface nanocrystallization and the effects of processing techniques and their parameters on surface nanocrystallization. Then, several methods for stabilizing nanocrystalline structures are briefly introduced. Furthermore, the review thoroughly examines the influence of surface nanocrystallization on the tribological properties and the underlying mechanisms. Finally, the potential applications and challenges of surface nanostructured configurations in friction and wear-related fields are thoroughly discussed.

The parallel connection of multiple flexible rings in raceways can significantly improve the electrical conductivity of rolling conductive devices. Multiple flexible rings are generally separated by idlers to form ring-idler rolling pairs. In the present work, alumina (Al2O3), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), and polyimide (PI) were used as idler materials. Rolling tests for four types of ring-idler contact pairs were carried out in the air at a rotating speed of 10 rpm and a current of 60 A. It was noticed that the voltage drop was the lowest when Al2O3 was incorporated as the idler material. The energy spectrum analysis indicated material transfer between the organic idlers and the flexible ring. Especially on the flexible ring surface, the transferred organic thin film covered the gold-plated layer of the flexible ring and affected the electrical contact of the flexible ring. The transfer of Al2O3 was not obvious, and the mass fraction of Au on the flexible ring surface after the rolling test was 93.1%. The above results could help in selecting the best idler material for high-power conductive rotary joints.