The new-type CoCrFeNiMoTi_x high-entropy alloy coatings were successfully devised and prepared on Q235 steel using laser cladding. Influence of Ti content on their microstructure and wear-resistance was studied systematically; the relevant mechanisms were deeply revealed. The CoCrFeNiMoTi_x coatings consisted of NiTi, FCC, and BCC phases, and with the increasing of Ti content, contents of BCC phase and FCC phase gradually increased and decreased, respectively. The CoCrFeNiMoTi₀.₇₅ coating had the highest hardness (950 HV), which was about 6.5 times higher than the substrate (Q235 steel, 150 HV). According to Archard law, metal materials’ wear resistance is generally proportional to hardness; thus, the CoCrFeNiMoTi₀.₇₅ high entropy alloy coating with the highest hardness showed the best wear resistance, exhibiting a wear mechanism of slight abrasive wear.

Refractory high-entropy or medium-entropy alloys (RHEAs, RMEAs) exhibit outstanding strength and hold significant promise for high-temperature applications. However, their pronounced brittleness at room temperature restricts their industrial application. Recently, the introduction of interstitial oxygen has proven effective in refining the microstructure and improving the mechanical properties of RMEAs. In this study, we investigated the effect of interstitial oxygen content ranging from 0.5 to 6 at.% on the microstructures and mechanical properties of TiZrNb MEA. The alloys display a single BCC structure, showing a dendritic crystal morphology. At an oxygen content of 4 at.%, the alloy shows a room-temperature compressive yield strength of 1300 MPa and compressive strain of over 50%, achieving a balanced strength and ductility combination. Moreover, it shows excellent high-temperature mechanical properties, with yield strength exceeding 500 MPa at 800 °C. The Toda-Caraballo and Labusch theoretical models were used in the study to clarify the strengthening mechanism of the alloys, and the theoretical yield strengths obtained by calculation coincided with the experimental yield strengths. This validation not only confirms that the primary strengthening mechanism is solid solution strengthening, but also proves the reliability of the model in predicting the mechanical properties of MEAs and provides a theoretical basis for the use of interstitial atoms to strengthen MEAs.

The CoCrFeNi₂Mo_x (x = 0, 0.4, 0.5, 1.0, x values in atomic ratio) high-entropy alloy coatings were designed and prepared on the Ti-6Al-4V substrate by laser cladding technology, their microstructures, and dry sliding wear resistance were studied in detail. When x < 0.4, the coatings were mainly composed of BCC solid solution phase, (Ni, Co)Ti₂ phase, and α-Ti phase. When x ≥ 0.4, the new σ phase appeared in the coatings. As the Mo content increases from 0 to 1.0, the hardness showed a trend of first increasing and then decreasing, especially when x = 0.5, the coating hardness reached its maximum (882 HV), which was 2.65 times the hardness of the Ti-6Al-4V substrate. The CoCrFeNi₂Mo_x high-entropy alloy coatings significantly improved the wear resistance of Ti-6Al-4V substrate, and with the increase in Mo content, the friction coefficient, widths/depths of worn tracks and wear rates of the coatings showed a trend of first decreasing and then increasing. In particular, when x = 0.5, the CoCrFeNi₂Mo_0.5 high-entropy alloy coating has the lowest friction coefficient (0.63), widths/depths of worn tracks (width: 803.690 μm; depth: 20.630 μm) and wear rate (5.136 × 10⁻⁵ mm³/(N·m)), which is one order of magnitude smaller than that of the substrate (3.694 × 10⁻⁴ mm³/(N·m)), demonstrating the best wear resistance. This is mainly because the appropriate proportion of hard α-Ti and σ phases effectively played a supporting role in resisting wear, while the relatively soft and dispersed BCC and (Ni, Co)Ti₂ phases could effectively prevent the occurrence of brittle fracture during wear test process.

Al_0.6CoFeNi₂V_0.5 high entropy alloy was successfully designed and prepared via the nonconsumable arc-melting process, and it was annealed at 600 °C, 800 °C, and 1000 °C for 4 h. Its microstructure and mechanical properties were studied. The as-cast alloy consisted of FCC and BCC phases, and no phase transformation occurred during annealing at 600 °C. Hard Al₃V-type metal compounds precipitated during annealing at 800 °C, and BCC particles precipitated in the FCC matrix during annealing at 1000 °C. After annealing, the strength and hardness of Al_0.6CoFeNi₂V_0.5 high-entropy alloy both showed a decreasing trend, because the annealing process eliminated the internal stress in this alloy. However, as the annealing temperature increased, the strength and hardness of the Al_0.6CoFeNi₂V_0.5 high-entropy alloy samples gradually increased. This is because the hard Al₃V metal compounds precipitated when the annealing temperature was 800 °C, which produced the “second phase strengthening” effect. At 1000 °C, the larger volume fraction of the hard and fine BCC phase (21.81%) diffusely precipitated; the precipitation of this BCC phase not only produced a “second phase strengthening” effect, which also resulted in “solid solution strengthening”, ultimately exhibiting enhanced hardness and strength. These findings have important theoretical reference value for the study of the microstructure and mechanical properties of high-entropy alloys. And, this study plays a significant role in promoting the research and development of new component materials that bear compressive loads, such as columns in large factory buildings, supports for cranes, and clamping bolts for rolling mills in practical mechanical engineering.

Review Application of Carbon Fiber Reinforced Aluminum Matrix Composites in Automotive Industry Wanmin Yu, and Li Jiang * School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China * Correspondence: jiangli@dlut.edu.cn Received: 10 February 2024; Revised: 4 June 2024; Accepted: 11 June 2024; Published: 20 June 2024 Although aluminum alloy has many excellent properties, it still has certain problems due to its strength and thermal deformation, which limits its application in the automotive industry. The carbon fiber reinforced aluminum alloy has the excellent characteristics of carbon fiber material and aluminum alloy material, with high strength, high modulus, high wear resistance and other characteristics, and has been extensively promoted in the automobile industry. This paper reviews the preparation process of carbon fiber reinforced aluminum alloy, including powder metallurgy, vacuum pressure immersion and squeeze casting. At the same time, carbon fiber reinforced aluminum alloy is introduced, mainly including automobile lightweight and the production of parts. This review paper will provide readers with a simple understanding of this field and offer some guidance regarding the application of carbon fiber reinforced aluminum alloy in the automotive industry.

The development of accident-tolerant fuels has significantly enhanced the safety of fission reactors. The TiNbZrO alloy system has garnered considerable attention due to its excellent mechanical properties and outstanding irradiation resistance. Its unique compositional design enables effective suppression of irradiation-induced defect formation. In this study, TiNbZrO thin films are fabricated via radio-frequency magnetron sputtering and irradiated with 50 keV He ions to fluences of 5 × 10¹⁶, 1 × 10¹⁷, and 2 × 10¹⁷ ions/cm². The microstructural evolution before and after irradiation is characterized by Transmission Electron Microscopy (TEM) and Grazing Incidence X-ray Diffraction (GIXRD), and the changes in mechanical properties are evaluated by nanoindentation. With increasing irradiation fluence, the average size of He bubbles increases from 1.10 nm to 2.06 nm, the number density decreases from 5.27 × 10²⁴ m⁻³ to 1.39 × 10²⁴ m⁻³, and the swelling rate rises from 0.37% to 0.64%. Although significant irradiation hardening is observed in all samples, the maximum hardening rate reaches only 31.91%, a value substantially lower than that reported for many conventional nuclear materials. This demonstrates the superior irradiation resistance of TiNbZrO thin films. The superior irradiation resistance of TiNbZrO thin films stems from two synergistic effects: high-entropy lattice distortion suppresses atomic diffusion, while oxygen complexes pin defects.