NbMoTaW and its derived refractory high-entropy alloys (RHEAs) exhibiting a single body-centered cubic (BCC) lattice structure have attracted widespread attention due to their exceptional strength at high temperatures. However, their practical applications are limited by room-temperature brittleness. While the BCC stability ensures resistance to thermal softening, its intrinsic high barrier to dislocation movements reduces the intrinsic ductility. Extensive research has been focused on mitigating this issue through microstructural and compositional modification. This review first discusses the fundamental mechanisms governing the brittleness in NbMoTaW and related BCC RHEAs, including grain boundary embrittlement, intrinsic properties and atomic environments. Then promising results from alloying and processing optimization are highlighted. Finally, the industrial feasibility and potential directions for alloy design and development are outlined.
High-entropy alloys (HEAs), composed of multiple principal elements, exhibit excellent mechanical properties, thermal stability, and resistance to phase transformations. However, their complex microstructural behavior challenges conventional processing and welding. This review summarizes recent advances in friction stir welding (FSW) and additive friction stir deposition (AFSD) of HEAs, focusing on microstructural evolution and mechanical performance. FSW promotes grain refinement with dynamic recrystallization, producing fine and homogeneous structures. Process parameters strongly affect heat input, where lower input improves the strength–ductility balance, while excessive input causes grain coarsening and property degradation. AFSD also enables grain refinement and strength enhancement through recrystallization and phase evolution. Further optimization and deeper understanding of phase evolution are required for broader industrial application.
This study explores how diamond particle size affects the thermal conductivity of diamond/Cu composites fabricated via high-temperature and high-pressure (HTHP) fusion infiltration method. Under extreme pressure, diamond particles (100–500 μm) undergo rearrangement and fracture, facilitating the infiltration of molten Cu into interstitial and internal gaps to achieve a diamond volume fraction >90%. The process also induces the formation of amorphous carbon on diamond surfaces, strengthening interfacial bonding. Consequently, diamond/Cu composites prepared via HTHP fusion infiltration method have higher thermal conductivity. A non-linear correlation between particle size and thermal conductivity was observed, with the optimal performance (606.33 W/(m·K)) attained using 200 μm diamond particles.
To protect WC-Co tools during machining, Ti/W-C/W-DLC compositionally graded coatings were deposited on YG12 cemented carbide via reactive magnetron sputtering. The effect of CH 4 flow rate (20–40 sccm) was systematically investigated. Results show a 30 sccm flow yields an optimized, dense sp 3 -rich amorphous structure with the lowest I D /I G ratio (0.82), suppressing W-catalyzed graphitization. This coating exhibits superior resistance to mechanical deformation and the highest interfacial adhesion (L c1 = 22 N). Furthermore, tribological tests demonstrate a low friction coefficient (∼0.09) and minimum wear rate (1.7 × 10 –7 mm 3 ·N −1 ·m −1 ). These findings elucidate hydrocarbon kinetics, providing a structural design strategy for highly wear-resistant cutting tools.
Hot-dip metallic sacrificial coatings is one of the most preferred solutions to enhance the corrosion performance of steels. The application of hot-dip Zn-Mg-Al (ZMA) coating for protecting steel structures from corrosion has gained significant attention in recent times owing to their superior corrosion resistance and mechanical properties compared to conventional zinc based hot-dip coatings. This succinct review examines the corrosion protection mechanisms of hot-dip ZMA coatings on steel substrates. The primary objective of the study is to comprehend the individual and synergistic effects of Zn, Mg, and Al on the microstructural evolution and corrosion behavior of the ZMA coatings. Further, the corrosion mechanisms of ZMA coated steel in chloride-rich aqueous environments are reviewed, in conjunction with the mechanism of black rust formation. Furthermore, this review examines key factors governing the long-term corrosion performance of the ZMA coatings and outlines emerging research directions to enhance their durability and environmental sustainability.
