JOM最新文献

Realizing the reliable bonding of tungsten (W) and reduced activation ferritic/martensitic (RAFM) steel is of significance for the fabrication of plasma-facing components in fusion reactors. Considering the significant differences in physical and chemical properties between the substrates of W and RAFM steel, the development of novel joining materials has attracted much attention in recent years. In the present work, a medium entropy alloy CoFeNi interlayer was selected to diffusion bond W and RAFM steel by utilizing an electric field-assisted joining technique. The effect of bonding temperature on the interface microstructure and mechanical properties of the joint was studied at room temperature. For the joints diffusion-bonded in the temperature range between 800°C and 1100°C for 15 min under 20 MPa, good metallurgical bonding without cracks and discontinuities were achieved at both the steel/CoFeNi and CoFeNi/W interfaces. Face-centered cubic (FCC) solid solutions were formed at the steel/CoFeNi interface, while both FCC and μ phases were identified at the CoFeNi/W interface. The W/CoFeNi/steel joint diffusion bonded at 900°C has the highest tensile strength of 313 MPa. Moreover, the comparison of the joint tensile strength between this work and previous researches has been discussed.

A comprehensive assessment of the quasi-static strength behavior of niobium (Nb)-based refractory systems, including the conventional Nb alloys and refractory high-entropy alloys (RHEAs), in a broad temperature range has been performed in this review. The strength and ductility data of the Nb-based refractory systems in varying temperature ranges manufactured by various methods have been compiled and discussed to correlate the manufacturing, material characteristics, deformation, and strength behavior. The microstructure characteristics and the interstitial contaminations have been identified as the dominating factors in controlling strength behavior in the low-temperature range of the Nb alloys. In the intermediate temperature range, the dynamic strain recovery plays a significant role in dictating the strength behavior, while, in the high-temperature domain, the diffusion-assisted deformation process leads to significant strength reduction. Nb-based RHEAs have been found to have great potential for applications in extreme temperatures (> 1200°C). A wide range of strength and ductility is possible in Nb-based RHEAs. Solid-solution strengthening largely controls the variation in strength, ductility, and thermal stability of RHEAs.

The titanium-coated alloy heterogeneous structure has been widely used in the manufacture of re-entry hypersonic vehicle wings. However, due to the extreme and complex hypersonic service environment, the strength of the Ti alloy matrix is easily reduced under the synergistic action of complex loads such as aerodynamic heat, vibration, corrosion, and noise. This results in a mismatch of structural strength at the interface structure in the titanium-coated alloy, leading to destruction of the wing aerodynamic shape. At the same time, multiple load synergies can also lead to defects such as cracks and holes in the surface coating, damaging wing structural integrity. In addition, under the combined action of frequency- and time-domain loads, the wing structure will also experience creep deformation, leading to fatigue–creep interaction, exacerbating the accumulation of wing damage, and posing a serious threat to the service safety of the re-entry hypersonic vehicle. Therefore, this paper first reviews current research hotspots of re-entry hypersonic vehicle technology, and then analyzes the strengthening–toughening mechanism, high-temperature fatigue behavior, high-temperature creep behavior, and the damage prediction model of the titanium-coated alloy’s heterogeneous structure. Finally, it summarizes and prospects future research directions.

The phase diagram information of the CaO-Al₂O₃-VO_x system is of significant importance for the direct alloying study of vanadium (V) during the smelting process of V-containing alloy steel, as well as for subsequent process optimization. This study has utilized the high-temperature phase equilibrium experimental method, combined with scanning electron microscope–energy dispersive spectrometer (SEM–EDS), electron probe micro-analysis (EPMA) and X-ray photoelectron spectroscopy (XPS) detection techniques, to research the phase equilibrium of the CaO-Al₂O₃-VO_x system under argon (Ar) atmosphere at 1400°C. This study reveals that the phase diagram of CaO-Al₂O₃-VO_x system, under the specified conditions, comprises 4 three-phase regions, 7 two-phase regions, and a liquid phase region. This study has plotted the CaO-Al₂O₃-V₂O₅-VO₂ three-dimensional phase diagram and represented the phase equilibrium in CaO-Al₂O₃-V₂O₅, CaO-Al₂O₃-VO₂, CaO-Al₂O₃-VO_2.335, and Ca-Al-V systems. At the same time, the reliability of each projected phase diagram was quantitatively assessed.

In situ monitoring is critical for developing new control methods, advanced materials and toolpath planning strategies in laser beam directed energy deposition (DED-LB). Coaxial melt pool monitoring has typically been performed with cameras [e.g., infrared, two-color pyrometer, charge-coupled device, or complementary metal-oxide semiconductor], which have focused on melt pool morphology and temperature distribution. While these techniques capture critical deposition information, they do not capture other important phenomena such as the unique coupling between the laser and melt pool, which limits the design and generality of open-loop and closed-loop process control. We establish in situ, parallel signals by monitoring multiple process phenomena at the same time through different wavelength bands and thermal correlation. Increased laser coupling was observed using in situ, parallel monitoring, where lower reflectivity/higher absorption of the laser light within a vapor depression led to an increase in thermal emission in the visible region. Ultimately, a relationship between each change in process parameter and the relative absorption of the laser was established. In situ monitoring of the laser coupling phenomena not only provides insight into material processing conditions but will also enable more complex control in DED-LB processes.

Weight reduction is critical in various engineering applications, as it directly impacts performance, efficiency, and overall cost-effectiveness. Topology optimization (TO) and lattice structures are effective methods for weight reduction, and such intricate designs are typically produced by additive manufacturing (AM). This research article presents an experimental investigation on the mechanical properties of uniform and gradient gyroid lattice structures manufactured through selective laser melting (SLM) using 17-4 precipitated hardening (PH) stainless steel (SS) material. The study focuses on analysing the effects of three different heat treatment processes on the compressive mechanical behaviour of the lattice structures using stress–strain graphs. Uniform lattices demonstrate superior mechanical properties by ensuring consistent structure stiffness and strength. Heat treatments decreased the grain size, resulting in increased yield strength for uniform and gradient structures compared to as-built samples. From the results, as-built samples showed higher plateau stress and energy absorption due to lower martensite content, leading to increased stress in the plateau region. Furthermore, different weight reduction methods such as TO, lattices, and the combination of TO and lattice can be studied and explained using an anchor bracket by utilising uniform and gradient-type sandwich lattice.