Shouren Wang

To improve the service reliability of high‐carbon bearing steels under complex alternating stresses, a novel heat treatment route combining double quenching and low‐temperature tempering was proposed in this study. The effects of this process on the microstructural evolution and four‐point bending fatigue behavior of GCr15 steel were systematically investigated. Multiscale characterization techniques, including SEM, EBSD, and TEM, were employed to elucidate the evolution of prior austenite grain structure, martensitic transformation behavior, and nanoscale carbide precipitation mechanisms. The results demonstrated that, compared with the conventional single‐quenching process, the double‐quenching treatment significantly refined the microstructure. The prior austenite grain size was reduced from 18.61 to 5.23 μm, and the martensite lath width decreased from 4.8 to 2.8 μm. EBSD analysis further revealed that the fraction of high‐angle grain boundaries increased from 26.55% to 35.83% after secondary quenching, thereby constructing an effective grain‐boundary barrier network. Four‐point bending fatigue tests indicated that the optimized microstructure fundamentally improved the fatigue performance. The crack propagation path exhibited frequent deflection, branching, and blunting due to the synergistic effects of grain boundaries, refined martensite laths, and dispersed carbides.

Flat-top pulsed fiber laser is used to clean the surface of 7050 aluminum alloy after anodizing. The optimal parameters for removing the anodized film are explored by changing the laser power, and various properties of the surface after laser cleaning with different parameters are studied. Additionally, combining formula analysis, two possible hypotheses are proposed to explain the reasons of the phenomena of grain size ratio variation. The results indicate that the optimal parameter for laser cleaning the anodic oxide film on 7050 aluminum alloy is at 195 W by scanning twice. Under appropriate laser cleaning parameters, various properties of the material such as roughness, wear resistance, hardness, corrosion resistance, and so on have been improved. The mechanism of removing the anodic oxide film by flat-top laser is predominantly based on ablation mechanism, which is different from that of Gaussian laser that primarily rely on the vibration mechanism. Laser cleaning can refine the grains and exhibit obvious anisotropy. The changes in the size ratio are related to the magnitude of the impact force and the heat absorbed by the surface, which may be related to the incomplete exposure of the areas covered by residual oxide films and to temperature and shock waves during incomplete cleaning. Additionally, there may be unknown effects involved in this process.

In this paper, a new type of passive anti-icing coating, i.e., interfacial lubrication coating, is proposed and investigated. The coating was prepared using the spin-coating or drop-coating method, and by adding hydrophobic and lipophilic modified particles to the hybrid resin to lock up the oil, which can significantly reduce the adhesion between the surface and the ice, thus effectively preventing icing. The study systematically characterized the surface morphology, wettability, anti-icing properties, mechanical properties and durability of the four interfacial lubrication coatings. The results show that the hybrid resin-based coating based on fluorinated ethylene–vinyl ester copolymer (FEVE) and polyurethane (PU) exhibits the best anti-icing performance, with ice adhesion as low as 11 kPa and an extended icing delay time of 779 s. Meanwhile, the coating shows excellent long-term stability with virtually no increase in the ice shear strength after being left on the surface for 6 months. The durability mechanism analysis showed that the adsorption of hydrophobic and lipophilic modified nanoporous SiO₂ on silicone oil and the structural properties of the coating with a dense surface and porous interior are the key factors for achieving the retardation of silicone oil release and maintain the lubricity. This study provides new ideas for the design of efficient and long-lasting anti-icing coatings.

Fluorapatite glass-ceramics (FGC) have been widely used in dental ceramics due to their excellent aesthetic properties and biocompatibility. In recent years, new synthesis methods, forming technologies, and the continuous optimization of performance attributes have driven the application of FGC in dental veneers, coatings, composites, and other restorations. This review summarizes the current research and applications of this material in the dental field and looks forward to its future optimization directions. The article focuses on five aspects: the development of preparation techniques for FGC; advances in their application in dental restoration shaping technologies; the performance advantages and limitations of these materials as dental materials; the current application status in veneers, coatings, composites, and other restorations; as well as the challenges in the current applications and prospects. In addition, additive manufacturing technology shows extremely broad application potential in FGC molding and applications. This review is hoped to provide strong guidance for the further application of FGC in the dental field, promoting the integration of related research and industry upgrades better to meet the needs of clinical practice and patients.

Ultrasonic surface rolling (USR) was applied to GCr15 steel with different static loads and passes to improve the friction and wear properties, and then the fretting wear mechanism of GCr15 steel after USR treatment was systematically investigated. The results showed that the specimens treated by the USR had lower surface roughness and significantly increased compressive residual stress and microhardness. Furthermore, severe plastic deformation occurred in the surface layer of the specimen, which refined the grains and increased the density of high- and low-angle grain boundaries. Besides, the results of the fretting test showed that the USR treated specimens had lower wear volume, dissipated energy, and steady-state friction coefficient. The fretting wear resistance increased with the static load and the number of passes. The fretting wear mechanism changed from abrasive wear and severe adhesive wear to slight fatigue wear and abrasive wear owing to the use of the USR treatment. Surface smoothing and hardening are responsible for the improvement in the fretting wear properties of GCr15 steel for USR treatment.

The microstructure evolution, corrosion resistance, and wear resistance of Al–18Si–4 Mg–2Mn–0.5Fe–xCu (x = 0,1,2,3,4,5 wt%) alloys prepared by laser additive manufacturing (LAM) process are studied. It is found that the addition of Cu not only produces Cu‐rich strengthened phase, but also promotes the precipitation of the second phase. With the addition of Cu, the corrosion resistance of the alloy decreases, which is due to the increase of potential difference caused by the increase of the strengthening phase. The addition of Cu can effectively inhibit corrosion cracking. The hardness and wear resistance of the alloy increase with the increase of Cu content under the synergistic strengthening of the Q‐Al₅Cu₂Mg₈Si₆ phase and Al₂Cu phase. When the Cu content is 3 wt%, the hardness and wear resistance of the alloy are the best. However, with the increase of Cu content, part of the Q phase is transformed into the Al₂Cu phase; this synergistic strengthening effect is weakened, and the hardness and wear resistance of the alloy are reduced, but still higher than that of the alloy without Cu addition, which indicates that the addition of Cu can effectively improve the hardness and wear resistance of the alloy.