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The new aluminum alloy Al–18Si–10Cu–10Ni–5Mn–5Mg (wt.%) prepared by laser-directed energy deposition (L-DED) process has excellent mechanical strength but poor ductility. In this paper, a T6 heat treatment is applied to it, aiming at the improvement of the material's ductility. The results show that after the T6 heat treatment, the original fine microstructure of the material is destroyed, and the phase composition changes. However, it is found that the formation of the nano-strengthened θʹ phase and the clear crystal orientation relationship between the θʹ phase and the α-Al matrix make the θ′ phase form a continuous grain boundary in the Al matrix, thus enhancing the strength and hardness of the alloy. It is worth noting that the microhardness is reduced slightly, but the residual stress is almost completely eliminated. The experimental results of mechanical properties show that the tensile strength and compressive strength of the material are reduced by 12 % and 17 % respectively after T6 heat treatment, but the ductility of the material is increased by 1.3 times, which is mainly attributed to the change of strengthening mechanism and the large and uniform second phase.

In this study, FeCrCoNiMo0.5W0.75 HEAs functional gradient materials were prepared by the direct energy deposition (DED) technique, and the phase transition, microstructure and mechanical properties of the materials along the building direction were investigated. The material realizes a transition from a single FCC phase to an FCC + TCP phase from the bottom to the top. The bottom and middle of the material are typical dendritic (DR)-interdendritic (ID) structures, and at the top, due to the precipitation of the eutectic structure σ phase and μ phase, the material transforms into a hypoeutectic structure of FCC + eutectic. According to the EBSD results, the interior of the material is mainly columnar crystals that grow vertically to the molten pool. This unidirectional columnar growth makes the material have a strong texture in the direction. In addition, a large degree of grain refinement is exhibited from the bottom to the top, with the grain size reduced from 19 μm to 6.5 μm. According to the TEM results, the density of dislocations is much higher near the phase and grain boundaries than in other regions, and dislocation entanglement is formed by the continuous accumulation of loose dislocations. The micro-hardness of the material increased along the construction direction up to 892.5HV0.5, and the material has good compressive strength up to 2041 ± 45 MPa. The material has excellent wear resistance and high-temperature wear resistance, forming a continuous oxide layer at 800 °C, which greatly reduces the friction coefficient and wear rate.

Ceramics are highly regarded in dental restorations owing to their favorable mechanical properties, chemical resistance, biocompatibility, and aesthetic features. Ceramic additive manufacturing (AM) technology has emerged as a promising solution that offers advantages over traditional techniques such as injection molding, die pressing, tape casting, and milling. Ceramic AM is, however, still under development, with new technologies and devices continuously emerging. This paper provides a comprehensive review of the latest research and applications of ceramic AM in dental restoration, focusing on the progress made within the past five years. Three perspectives are discussed: ceramic AM technologies, commonly used printable ceramic materials, and different types of dental restorations. Among these, vat photopolymerization is the most widely researched and promising AM technology for large-scale applications. ZrO2 remains the primary material used in AM research, whereas crowns and bridges are the most frequently studied and are the closest to industrialized dental restorations. Currently, ceramic AM satisfies the clinical requirements of accuracy, mechanical performance, and biocompatibility. However, compared with traditional methods, it lacks significant advantages in terms of cost and manufacturing efficiency, limiting its large-scale application. Further improvements are necessary in all stages, including raw materials, equipment, post-processing, and standardization.

Abstract The research on surface texture is developing from single macro-texture to composite micro-nano texture. The current research on the anti-friction mechanism and theoretical models of textures is relatively weak. Studying the characteristics of different types of surface textures and determining the applicable working conditions of each texture is the focus of current research. In this paper, a mathematical model of hydrodynamic lubrication is established based on Navier–Stokes equations. The FLUENT software is used to simulate and analyze the four texture models, explore the dynamic pressure lubrication characteristics of different texture types, and provide data support for texture optimization. The key variable values required by the mathematical model are obtained through the simulation data. The friction coefficient of the texture under different working conditions was measured through friction and wear experiments, and the mathematical model was verified by the experimental results. The research results show that circular texture is suitable for low to medium speed and high load conditions, chevron texture is suitable for medium to high speed and medium to high load conditions, groove texture is suitable for high speed and low load conditions, and composite texture is suitable for high speed and medium to high load conditions. Comparing the experimental results with the results obtained by the mathematical model, it is found that the two are basically the same in the ranking of the anti-friction performance of different textures, and there is an error of 10%−40% in the friction coefficient value. In this study, a mathematical model of hydrodynamic lubrication was proposed, and the solution method of the optimal surface texture model was determined.

This article reviews the current status of automotive brake disc research and the prospects for future research. At present, the research of brake disc performance mainly includes thermal conductivity, thermal fatigue resistance, wear resistance, and brake noise. It is found that a new alloy composite, heat treatment process, ceramic composite, new structure, and new materials are emerging. At the same time, it was found that ceramic and resin were used as the matrix, fiber materials were used as reinforcements to prepare brake discs, the addition of new fillers and the study of special reinforcement materials have become new hotspots in the study of brake discs. In the future development, carbon-fiber ceramic brake discs may become the main research focus of brake discs.

A new type high temperature self-lubrication TiC/FeCrWMoV metal ceramic was fabricated successfully by applying an innovating technology which molten solid lubricant (60Pb40Sn-15Ag-0.5RE) was infiltrated into metal ceramic preforms with an interpenetrating network using a vacuum high pressure infiltration furnace. The friction and wear behaviors of the composites were investigated using a pin-on-disk high temperature wear testing machine at different temperature (up to 800°C). The compositions, images and structures of worn surfaces were analyzed by means of scanning electron microscope (SEM), energy dispersive X-ray analysis (EDXA) and X-ray diffraction (XRD). The self-lubrication mechanisms of the composites were discussed. The experimental results indicated that during elevated temperature sliding, the solid lubricants were squeezed out of the micropores to the frictional surfaces to form PbMoO4, PbO, SnWO4, Ag2WO4 and Ag3Sn. The formation of lubrication film containing of these oxides and of intermetallic compounds was the main reason that the composites had good self-lubrication properties at high temperature. It was considered that the micro-pores on friction surface would be the crucial factors determining the self-lubricating properties of the self-lubrication composites.