Low friction at high temperature remains a challenge for traditional solid lubricant due to high temperature oxidation and degradation. In this work, we develop a novel silicate glass lubricant to realize low friction (below 0.1) from 750 to 850 °C, representing a 79% reduction compared to dry sliding condition. Interfacial evolution analysis revealed a novel “reaction-induced self-anchoring” mechanism for enhanced lubrication performance: chemical reactions between Ca2 + in the glass phase and TiO2 in the substrate oxide layer induced in-situ precipitation of CaTiO3 micro-protrusion crystals at the interface. These crystals function as “anchors”, significantly enhancing wettability and interfacial bonding strength. This effectively inhibits the dewetting and delamination of the lubricating film under high shear stress. Furthermore, the formation of a "ceramic-glass" composite structure at the interface synergistically improves high-temperature load-bearing capacity. This unique interfacial architecture ensures structural integrity of the lubricating layer and elevates its high-temperature lubrication performance, providing a novel strategy for designing high-performance lubricants under extreme conditions.

In this study, AlCrFeNiMo high-entropy alloy (HEA) coatings have been successfully fabricated by laser cladding method using the mixed elemental powders as the raw material. Two different laser powers (200 W for HEA1 and 350 W for HEA2) were used, aiming to investigate the influence of processing parameters on the phase constitution, microstructure and properties of as-cladded HEA coatings. It has been found that both AlCrFeNiMo HEA coating is consisted of BCC1, BCC2 and Mo-rich phases. HEA2 exhibited finer microstructure, reduced elemental segregation, and slightly higher hardness (833.3 HV) compared to HEA1 (808.6 HV). Tribological testing from room temperature to 900 degrees C showed that HEA2 consistently achieved lower friction coefficients and wear rates with lowest values of 0.29 and 0.68 x 10-5 mm3/Nm at 900 degrees C, respectively. Cross-sectional and surface analyses revealed a transition from abrasive wear at room temperature to oxidative wear at 900 degrees C, with HEA2 forming a denser, stable tribo-oxide layer enriched in Al and Cr. These results highlight that optimizing laser processing enhances the microstructural integrity and high-temperature wear resistance of AlCrFeNiMo HEA coatings, making them promising for extreme service conditions.

Understanding of wear behavior in dual-side graphene coatings is essential for the reliable design of nanomechanical systems. In this study, molecular dynamics simulations are employed to investigate the effect of surface roughness (SR) matching on the nanoscale wear response of dual-side graphene-coated interfaces. Key parameters, including critical wear load, peak friction force, stress distribution, and graphene bending angle, are systematically evaluated under both matched and mismatched SR conditions. The results reveal a correlation between roughness compatibility and nanowear performance. Specifically, SR matching leads to balanced stress distribution and comparable critical wear loads on both contacting surfaces, resulting in more uniform and predictable wear behavior. In contrast, mismatched SR conditions cause stress asymmetry and localized deformation, making the graphene layer on the rougher surface more prone to damage. These findings enhance the understanding of nanowear mechanisms in graphene-based coatings and offer a quantitative basis for optimizing their durability and performance in advanced engineering applications.

This study presents a comprehensive investigation of the short-term isothermal oxidation behaviour and tribological performance of a FeCr2VW0.3 refractory medium-entropy alloy (RMEA) with dual BCC phases from room temperature (RT) to 650 degrees C. The RMEA exhibits excellent oxidation resistance below 550 degrees C, while noticeable oxidation occurs at 650 degrees C. Both friction coefficient and specific wear rate decrease when temperature is increased from RT to 650 degrees C; notably, the wear rate at 650 degrees C is reduced to approximately 3.85% of that at RT. Surface profilometry and SEM observations reveal obviously smoother worn surfaces at elevated temperatures, accompanied by a marked reduction in spallation and delamination and the formation of a relatively continuous and compact tribo-layer. SEM and TEM cross-sectional analyses identify three distinct regions along the depth direction at all temperatures: a topmost tribo-layer, a middle severe plastic deformation region, and a lower less deformed region. With increasing the temperature, the topmost layer evolves from a porous tribo-layer composed of mixed wear debris and oxides at RT to a relatively dense and continuous protective tribo-layer at 650 degrees C. Moreover, at RT, the severe plastic deformation region consists of nanograined BCC1 phase mixed with fractured coarse-grained BCC2 phase, whereas crack density within the BCC2 phase decreases markedly at 650 degrees C while the BCC1 phase remains nanograined. The superior thermal-mechanical properties of the alloy, combined with the formation of a stable tribo-layer, lead to a transition in the wear mechanisms from abrasion, plastic deformation, delamination and spallation dominated wear at RT to oxidative and adhesive wear at elevated temperatures.

High-temperature tribology is a multidisciplinary science that has evolved rapidly in response to the increasing performance demands of high-technology sectors, including aviation, aerospace, nuclear energy, power generation, and advanced metal forming industries [...]

Although high-entropy alloys (HEAs) exhibit excellent comprehensive properties, their practical application remains constrained by the inherent strength-ductility trade-off. In this work, a hierarchical duplex heterostructured Fe39Ni37Cr8Si8Al8 HEA with mutual precipitation behavior was developed, which effectively alleviates this trade-off. After cold rolling and short-time annealing at 900 degrees C, a laminated microstructure consisting of alternating face-centered cubic (FCC) and body-centered cubic (BCC) lamellae was formed. The FCC lamellae contain dispersed submicron coherent B2 precipitates, while the BCC lamellae concurrently precipitate a locally high density of fibrous coherent FCC particles. This mutual-precipitation behavior results in a multiscale interfacial network and exceptional mechanical properties, achieving an ultimate tensile strength of similar to 1819 MPa with an elongation of similar to 15%. Such performance arises from synergistic strengthening mechanisms, including hetero-deformation-induced hardening at FCC/BCC lamellar interfaces, dislocation pinning by B2 precipitates in the FCC lamellae, and improved deformation compatibility enabled by the "segmentation-refinement-toughening" effect of FCC fibrous precipitates in BCC lamellae. This study elucidates the crucial role of mutual precipitation in achieving high strength-ductility synergy, which presents a new design strategy for next-generation advanced structural materials.

The grain refinement of high-stacking-fault-energy metals during high-pressure torsion (HPT) is governed by dislocation activity and boundary evolution. However, how local misorientation evolves during different stages of grain refinement remains insufficiently clarified. In this study, AA1050 aluminium was processed by HPT to selected equivalent strains of 0, 0.90, 2.69, 10.76 and 53.78, and electron backscatter diffraction (EBSD) was used to analyse grain morphology, boundary fractions and EBSD-derived misorientation parameters. The results reveal strongly stage-dependent grain refinement during HPT. The average grain size decreases rapidly from 12.63 μm in the initial state to 3.29 μm at ε = 0.90 and 2.19 μm at ε = 2.69, remains nearly unchanged at ε = 10.76, and finally decreases to 0.58 μm at ε = 53.78. The fraction of low-angle grain boundaries increases markedly at ε = 0.90, indicating intensive formation of dislocation substructures, whereas high-angle grain boundaries become dominant at high strain. Grain orientation spread (GOS) and grain reference orientation deviation (GROD) exhibit non-monotonic evolution, whereas the geometrically necessary dislocation (GND) density increases markedly at the early deformation stage and subsequently decreases with further deformation. These results indicate that the stage-dependent grain refinement of AA1050 during HPT is closely associated with dislocation-mediated grain subdivision involving alternating grain elongation and fragmentation.

In this study, four vanadium (V) containing high entropy alloys (HEAs) Al0.5CrFeNiVx (x = 0.25, 0.5, 0.75, 1.0) were developed and investigated, in terms of examining the influence of V content on their microstructure, insitu oxidation behavior, high temperature mechanical strength, and high temperature tribological performances. An increase in the V content causes precipitation of the Laves phase (VAl2) in the body-centered cubic (BCC) matrix. This structural transition increases the alloy hardness and compressive strength through solid solution strengthening, precipitation strengthening and grain refinement strengthening. When x is increased from 0.25 to 1, the maximum compressive strength increases from about 2476 to 3241 MPa at room temperature and from about 521 to 797 MPa at 700 degrees C, respectively. In-situ oxidation investigation reveals that a higher V content accelerates the oxidation and provides a direct evidence of vanadium oxides melting at 700 degrees C and thus forming the liquid oxide phases on the surface of HEAs. During high temperature tribological contact, the liquid oxide phases minimize the friction, allowing thicker and more complex oxide layers to form on the worn surface to improve the HEAs' wear resistance. The findings in this work contribute to the development of novel HEAs with superior properties for potential applications that need outstanding mechanical strength, wear resistance, and thermal stability.

Fabrication of Al/Ni multilayer sheets with great layer continuity has always been a challenge due to early necking and rupture of Ni layer in rolling process, which usually results in a structure with Ni fragments in Al matrix and induces poor thermal performance. This study investigates the fabrication and characterization of Al/ Ni multilayer sheets with a focus on achieving excellent layer continuity. The multilayers were prepared using accumulative pack rolling (APR) and roll bonding techniques, combining aluminum alloys (AA1050 and AA7075) with Ni to form laminated composites with controlled thickness ratios. The mechanical compatibility between materials by heat treatment and warm roll bonding was emphasized to mitigate plastic instability, such as shear banding and necking, which disrupt layer continuity. Differential scanning calorimetry (DSC) was employed to evaluate the thermal performance and the formation of intermetallic compounds, including Al3Ni and Al3Ni2. The results indicate that AA7075/Ni multilayers exhibit excellent structural integrity and thermal response compared to AA1050/Ni. While achieving bilayer thicknesses as thin as 5-10 mu m, the study also highlights the issues of bonding quality in thinner layers and the impact of thickness ratios on heat release efficiency. This work demonstrates the potential of heat treatment and warm roll bonding as cost-effective, scalable methods for fabricating high-performance AA7075/Ni multilayers and provides valuable insights into optimizing their design for thermal and mechanical applications.

This study investigated the effects of oxygen doping on the mechanical and tribological properties of Ni55Ti45 alloy at high temperature. It was found that adding 2 at%O increased the alloy's hardness by 22 % and reduced the friction coefficient to 0.286. At 500 degrees C, the wear rate of the oxygen-doped alloy was reduced to 0.38 x 10-5 mm3 /(m N), exhibiting the best wear resistance. These improvements were attributed to the in-situ formed precipitated oxide phases and glaze layer induced by the shear force during the friction process at high temperature. The wear mechanism transitioned from abrasive wear and fatigue delamination at RT to oxidation wear at 500 degrees C. This work demonstrated that oxygen doping is an effective strategy to improve the high temperature tribological properties of Ni55Ti45 alloy.

This study explored the potential of rice husk ash (RHA) with high dosage as an replacement of cement for developing ultra-high performance concrete (UHPC). The mechanical properties, durability, microstructure, as well as the heavy metal ions solidification properties were subjected to systematic research and analysis. Results show that replacing cement with 40 % RHA reduces its fluidity to 163.6 mm, yet still maintains good fluidity, facilitating the effective setting of the concrete, with a compressive strength and flexural strength of 118 MPa and 21.9 MPa, respectively. With the reduction in RHA particle size, the hydration products such as C-S-H gel and ettringite were increased. When the RHA particle size is 5 mu m and the dosage is 5 %, the optimal mechanical and impermeability properties are attained. At the curing age of 28 days, the maximum compressive strength and flexural strength are 136.24 MPa and 24.7 MPa respectively, and the impermeability improvement rate is 85.5 %, suggesting that the incorporation of RHA is conducive to the enhancement of the mechanical and impermeability properties of UHPC. Meanwhile, it can be concluded that the microstructure of the pores is filled and refined by the generation of hydration products such as C-S-H gel, thereby reducing the total porosity by up to 27.8 %. The intrinsic elastic modulus of RHA particles, which is approximately 7 GPa, is significantly smaller than that of most hydration phases present in the UHPC mixture. Additionally, when the dosage of RHA reaches 40 %, it can significantly enhance the solidification of heavy metal ions in UHPC, minimizing the negative impact of UHPC on the environment. The utilization of high proportions of RHA as an auxiliary cementitious material in the development of UHPC not only holds extensive application prospects but also builds upon current research integrating RHA into conventional concrete. This study is instrumental in bridging the gap towards green and sustainable development within the international research landscape for UHPC materials.

While the single-particle impact model is widely used in studying the high-velocity impact behavior of particles, its scope is limited to the interaction between an individual particle and the substrate. In this work, a multi-particle molecular dynamics model was established to investigate the impact behavior of Cu nanoparticles and the surface quality of coatings. It was found that with the increase in particles' impact velocity from 100 m/s to 1500 m/s, three distinct coating structures can be identified: adhesion between nanoparticles, co-deformation, and liquefaction. Due to the anisotropy of plastic deformation, coatings formed by particles with the initial orientation [110] displayed the roughest surface, while those aligned with [111] and [001] exhibited smoother surfaces. Additionally, as nanoscale particles possess limited kinetic energy, it is difficult to create a large crater on the surface of the substrate. Therefore, it was necessary to elevate the temperature to soften the substrate, which can increase the crater depth and improve bonding quality. A successful approach to enhancing the bonding strength and surface quality of coatings involves simultaneous optimization of impact velocity, crystallographic orientation of particles, and substrate temperature.

In this study, a new V-containing high-entropy alloy (HEA) with the chemical composition of Al0.5CrFeNiV0.5 has been developed. Its microstructural features and phase constitutions were investigated by several techniques, including X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The as-cast Al0.5CrFeNiV0.5 HEA exhibits an average Vickers hardness of around 570.5 HV, a compressive strength of about 2.53 GPa and a plasticity of around 22.1 %. In addition, the HEA still exhibits very high compressive strength of about 1218.6 MPa at 600 degrees C, but it decreases quickly to around 586 MPa at 700 degrees C and 301 MPa at 800 degrees C. On the other hand, high-temperature sliding wear tests of as-cast HEA against the Si3N4 ceramic balls revealed a slight change of friction coefficient in a range of 0.4-0.5 between RT and 800 degrees C. However, the wear rate of HEA was found to increase monotonically with increasing the temperature, and was particularly higher when temperature exceeded 600 degrees C. The associated mechanisms have been discussed in details based on chemical composition analysis, worn surface morphology observations as well as the characterizations of the wear track cross-sections.

Ultrathin copper foils (thickness less than 50 mu m) with controlled surface roughness are essential in modern electronics, improving performance and reliability in applications such as lithium-ion batteries and printed circuit boards (PCB). Proper surface roughness enhances resin adhesion in PCB lamination, while thin foil thickness reduces weight and increases energy density in battery collectors. Accumulative pack rolling (APR) is a novel severe plastic deformation process capable of imposing large strain to fabricate ultrathin copper foils with tunable surface roughness. Using a 0 degrees pack arrangement, APR successfully produced ultrathin copper foils of 2.2 mu m thickness, whereas a 90 degrees pack arrangement obtained thicker copper foils (11 mu m) with high surface roughness (Ra similar to 4.5 mu m). Differences in foil thickness were attributed to through-thickness pinholes caused by increased roughness, reported here for the first time in this processing type. Surface roughness increase is linked to Cube soft orientations with weaker tensile properties. During deformation, these orientations remain or increase, becoming strain incompatible with harder orientations such as S, Brass, and Dillamore. This incompatibility leads to shear bands, acting as geometric softening mechanisms that distort lamellar structures, propagate across interfaces, and transmit strain localization into adjacent foils, resulting in out-of-plane displacement. This intrinsic deformation-induced roughening mechanism allows copper foils to achieve customizable surface properties without additional roughening treatments. These advantages position APR as a competitive method for electronic materials manufacturing.

Medium manganese (Mn) steels, noted for their cost efficiency and exceptional mechanical properties, are particularly suitable for cutting-edge engineering applications. This study delivers an exhaustive analysis of medium manganese steel, detailing its thermal and mechanical treatment methods, prospective challenges, and the intrinsic factors attributing to its superior strength and ductility. Notably, deep cryogenic treatment is gaining favor over traditional hot and cold rolling methods. The retained austenite grains display diverse mechanical stabilization, promoting a gradual shift to martensite during deformation. Enhanced by this transformation, the TRIP (Transformation-Induced Plasticity) effect is significantly amplified, contributing substantially to the enhancement of the material's mechanical properties. The specifically targeted medium manganese steels have been successfully synthesized in the lab, demonstrating tensile properties in select samples that exceed projected standards. Accordingly, a carefully calibrated chemical composition, in conjunction with the strategic employment of toughening mechanisms, ensures exceptional toughness at low temperatures while also realizing high tensile strength.

A new high-entropy alloy (HEA) based self-lubricating composite with good mechanical and tribological properties has been designed and fabricated, using Al0.5CrFeNiV0.5 HEA as matrix and hexagonal boron nitride (hBN) as solid lubricant. In addition to the well dispersed hBN particles, the novel composite is consisted of (Al,Ni)-rich, (Cr,V)-rich, (Cr,Fe,V)-rich, CrVB4, and AlN phases. High temperature nanoindentation tests of the composite revealed its excellent thermal softening resistance, showing very good mechanical strength stability in a wide temperature range. Additionally, the composite also exhibits substantial improvements in friction reduction and anti-wear performance from RT to 700 degrees C. The enhanced mechanical and tribological properties are attributed to the hBN and new phases formed by reactions between hBN and Al0.5CrFeNiV0.5 HEA matrix. The main wear mechanisms during sliding of the Al0.5CrFeNiV0.5-hNB composite against the Si3N4 balls shift from abrasion and plastic deformation to oxidation and adhesive wear as the wear testing temperature is increased.

This study explores the feasibility of cladding CrFeNiAl0.3Ti0.3 and CrFeNiAl0.3Ti0.3–Ag high entropy alloys, produced via hot-press sintering (HPS), with commercial mild steel using the hot roll bonding (HRB) method. The bonding interface characteristics, mechanical properties, and tribological performance of these laminated composites were systematically evaluated. Microstructural analysis revealed that both high entropy alloys formed good metallurgical bonds with mild steel, exhibiting a straight interface free of visible cracks and oxidation products. Tribological investigations demonstrated that hot rolling significantly enhanced wear resistance, with specific wear rates decreasing by 70–82

Recent years have witnessed a transformative shift with the advent of high entropy alloys (HEAs), liberating the constraints on the composition of high-strength alloys. Nevertheless, the composition design of most HEAs still relies on “trial-and-error” approaches either experimentally or computationally. Given the expansive composition space inherent to HEAs, the conventional “trial-and-error” method poses a formidable challenge in pinpointing potential high-performance HEA compositions. Here, we implement a “self-optimizing” strategy to minimize the arduous “trial-and-error” approach. The “self-optimizing” strategy involves identifying the chemical composition of supersaturated single solid-solution phases by directly using the local compositions of specific phase constituents within existing multicomponent alloys containing dual or multiple phases. The “self-optimized alloy” exhibits enhanced tensile mechanical properties with a yield strength of around 1.2 GPa and appreciable ductility up to around 10%. The enhanced yield strength stems from a unique multi-scale hierarchical microstructure and the resulting multistage deformation behaviour and integrated strengthening effects. The strategy of “self-optimized alloy” design and hierarchical microstructure control are readily applicable to other existing dual-phase or multi-phase alloys, expediting the exploration of novel advanced engineering materials.