The manufacturing of high-quality MCrAlY bond coats is crucial for the durability of thermal barrier coatings (TBCs). Although atmospheric plasma spraying (APS) offers a flexible and efficient deposition route, it has traditionally been considered unsuitable for MCrAlY bond coat deposition due to the high oxide content. In this study, NiCoCrAlY bond coats with low oxygen content were successfully prepared via APS by adding carbon as a deoxidizing agent to the feedstock powder. The effect of carbon content in the powders on the thermal cycling lifetime of TBCs, comprising yttria-stabilized zirconia (YSZ) top coats and APS-deposited NiCoCrAlYC bond coats, was systematically investigated through isothermal thermal cycling tests, with comparisons made to TBCs using low-pressure plasma-sprayed (LPPS) NiCoCrAlY bond coat. The results indicate that the APS-processed NiCoCrAlYC bond coat exhibits a dense microstructure with low oxide content. TBCs with the APS bond coat displayed the same failure mechanism as those with an LPPS bond coat. Remarkably, despite slightly lower Al content, TBCs with the APS bond coat achieved a 16 % longer thermal cycling lifetime than those with an LPPS bond coat. The formation of a continuous, dense alpha-Al2O3 scale, coupled with the precipitation of Cr7C3 carbide particles in the bond coat, led to this improvement by alleviating the thermal expansion mismatch between the top coat and the superalloy substrate. This work demonstrates the feasibility of using APS as a substitute for LPPS in producing high-performance MCrAlY bond coats for TBCs with enhanced thermal cycling resistance.

Pore-free and fine-grained microstructures are key points for laser ceramics. In this paper, high-quality Yb: YAG laser ceramics were prepared by pre-sintering in vacuum followed by hot isostatic pressing (HIP) post-treatment. The influences of two different pre-sintering methods (normal sintering (NS) and two-step sintering (TSS)) on the microstructure and optical properties of YAG ceramics were studied. The ceramics pre-sintered by TSS could reach higher density and smaller grain size with lower holding temperature than NS method. Accordingly, the highest transmittance of TSS/HIPed specimens were 83.3% at 400 nm. Then, 2 at.% Yb: YAG transparent ceramics with a size of Φ20 mm × 5.5 mm were obtained by TSS/HIP process. The average grain size is 1.9 μm, while the transmittance reaches 83.2% at 400 nm. Moreover, the laser output test revealed that pump-output power curve of 2 at.% Yb: YAG ceramics is close to that of single crystal. Namely, the maximum output power and optical-to-optical conversion efficiency of 2 at.% Yb: YAG ceramics are 13 W and 39%, respectively. Hence, the combination of TSS in vacuum and HIP post-treatment is a promising process for the preparation of high-quality laser ceramics.

This study investigated the influence of solution-aging treatment (SAT) on the hydrogen embrittlement (HE) of selective laser melted 17-4 PH stainless steel. It was found that the as-printed steel exhibits a martensite/ austenite duplex phase microstructure with fine grains, which provides abundant grain boundaries/phase boundaries serving as hydrogen traps, thereby exhibiting a low hydrogen diffusivity. During SAT process, complex microstructural evolution such as grain coarsening, precipitation of nano-sized NbC/s-Cu particles, and gamma-*alpha ' phase transformation occurred in the steel. Collectively, these evolutions induced the hydrogen diffusion coefficient increasing first and then decreasing with the rise of solution temperature. Quantitively analysis revealed that the impact of austenite on hydrogen diffusion exceeds other microstructural factors. The mechanical test results show that SAT plays dual impacts on the hydrogen-assisted fracture, causing HE susceptibility to show a complex change of first increasing and then decreasing with increasing solution temperature. The advantage lies in that the precipitation of the nano-phase not only inhibits hydrogen-assisted intergranular cracking by serving as deep hydrogen traps, but also hinders dislocation movement to inhibits hydrogenenhanced localized plasticity. Conversely, the disadvantage lies in that the increase in martensite content, grain coarsening, and the gradual increase in the fraction of E3 boundary in the martensite phase collectively reduce cracking resistance, exacerbating HE fractures.

Selective laser melting was used to tailor the microstructure of 17-4PH stainless steel through scan-path superposition within a single build. Three strategies were evaluated: single-band scanning (SBS), stripe–checkerboard scanning (SCS), and alternating checkerboard–stripe scan (ACS). SCS achieved a tensile strength of 1190 MPa and improved elongation from 16.22

Ball milling parameters, including milling media and ball milling time (BMT) have significant effects on the final properties of TiCN-based cermets. In this study, a series of TiB2-reinforced TiCN cemerts was fabricated using ZrO2 balls, followed by spark plasma sintering (SPS) at 1600 degrees C for 10 min under a pressure of 35 MPa from a TiCN-Ti-Co-B4C system. The synergistic effects of BMT and ZrO2 incorporation during the ball milling process on the microstructure and properties of TiCN-TiB2-Co cermets were investigated. The results showed that prolonging BMT markedly increased the ZrO2 content in the composites. The peeled ZrO2 particles exhibited good chemical compatibility with the matrix and an extremely fine particle size. Extended BMT effectively refined the hard-phase grain size and promoted sintering. The as-sintered cermet subjected to 18 h of ball milling exhibited the densest microstructure. Both Vickers hardness and fracture toughness initially increased and then decreased with increasing BMT, with optimal overall performance achieved at 12 h of ball milling, corresponding to a hardness of 1923 HV and a fracture toughness of 7.51 MPa m1/2. The enhancement in toughness can be attributed to the combined effects of grain refinement, crack deflection, crack bridging, grain pull-out, and fracture mode transformation. Additionally, the cermet ball-milled for 12 h showed the best wear performance owing to its well-distributed microstructure and an optimum balance between hardness and toughness. However, excessive prolongation of BMT led to ZrO2 accumulation, and the significant mismatch in thermal expansion coefficients between ZrO2 and the matrix accelerated the microcrack formation and propagation, thereby impairing the mechanical properties and ultimately deteriorating the wear resistance.

As an emerging solid-state material deposition method, cold spray technology enables the deposition of metals in the solid state through the high-velocity impact (300-1200 m/s) of micron-sized powder particles (5-50 μm), avoiding the composition changes and microstructural/performance degradation associated with high-energy beam deposition processes. This paper systematically reviews recent advances in this technology from three dimensions: deposition mechanisms, performance control, and additive manufacturing. Regarding deposition mechanisms, particle interfacial bonding is primarily achieved through three key processes: the rupture of the surface passive film, exposure of fresh metal, and metallic bond formation. Reducing powder oxygen content (<0.1%) and increasing interfacial plastic deformation are key to improving bonding quality. In terms of performance control, composite processes such as laser-assisted cold spray and micro-forging have achieved favorable strength-ductility match in pure copper deposits (strength 220–250 MPa, elongation 30–35%). Nickel-based superalloy deposits exceed 99.6% density with tensile strength surpassing 850 MPa. For additive manufacturing, this technology has enabled the rapid fabrication of meter-scale components (up to 4.5 m). However, challenges remain in enhancing titanium alloy deposit plasticity (<2%) and controlling forming accuracy (tolerance > ±1 mm). In equipment development, commercial systems now achieve operating parameters of 10 MPa/1100°C with nozzle lifetimes exceeding 1000 hours. Although cold spray technology offers unique advantages for fabricating low-oxygen-content metal components in ambient environments, breakthroughs in dissimilar material bonding and intelligent process control are needed to promote its large-scale application in high-end manufacturing fields such as aerospace and defense.

High-entropy alloys (HEAs) exhibit the outstanding properties, owing to the multi-principal-element design and high-entropy effects. Nevertheless, the conventional forming processes of HEAs fail to produce the complex shapes while maintaining the microstructural uniformity, hindering the industrial application. Additive manufacturing (AM) provides the revolutionary solution for complex component forming and microstructure precision control. The research status of mainstream additive manufacturing technologies used for high-entropy alloy preparation was systematically reviewed in this paper, such as laser powder bed melting and directional energy deposition. The typical systems, microstructure characteristics, mechanical properties, and functional properties of additive manufacturing high-entropy alloys were summarized. The AM technology can refine grains, inhibit harmful phases, promote the formation of metastable phases, and significantly improve material properties through rapid solidification and thermal cycling. However, the challenges still remain, such as complex process parameters, crack sensitivity, high preparation cost, and insufficient multi-scale simulation. In the future, the machine learning should be actively used to optimize the process-organization-performance relationship, develop new AM technology and post-treatment process, design low-cost alloy system, and realize the intelligent design combined with cross-scale simulation.

Cold spray, conventionally a powder consolidation process to deposit materials, shares many attributes with the shot peening process that is used to strengthen metal surfaces. It is possible to take advantage of the high particle impingement velocity achieved by the cold spray equipment and use the process as a high-velocity shot peening process to strengthen metal surfaces. Cold spray shot peening (CSSP) is an emerging surface engineering technique that integrates the high-velocity particle impact of cold spray with shot peening to enhance the mechanical properties of metallic materials. In this work, interstitial-free (IF) steel was used to explore the potential of CSSP in enhancing material surface and its mechanical properties. Results show that after different numbers of passes of CSSP, gradient microstructure was obtained, and grain refinement was achieved in the surface region. Repeated bombarding of the IF steel surface can increase its surface hardness by 53

To address the issue of brittle intermetallic compounds (IMCs) readily forming at the interface of lightweight magnesium/aluminum composites, which hinders their application in automotive and aerospace sectors, this study investigated the modification effect of adding a 0.1-0.3 mm Zn interlayer to aluminum-core/magnesiumshell magnesium/aluminum composites. Results indicate that the Zn interlayer reduces the thickness of brittle Mg-Al intermetallic compounds (IMCs) at the interface by 60 % through the formation of ductile Mg-Zn phases (e.g., MgZn transition layers). Simultaneously, it increases the interfacial shear strength from 20.8 MPa in the control sample to 38.8 MPa (an 87 % increase). Its diffusion barrier function effectively inhibits direct Mg-Al interaction. This study confirms that adding a Zn interlayer is an effective strategy to improve interface compatibility and enhance the performance of aluminum-core/magnesium-shell composites, providing key technical support for the practical application of such materials.

CuCrZr alloy is widely used in components with high heat flux, but its strength and high-temperature thermal conductivity still lag behind the actual application requirements. Additive manufacturing offers design freedom, but the coarse grains and coarse nanoprecipitates formed during the rapid cycling process of electron beam powder bed fusion (EB-PBF) severely weaken the mechanical properties of the samples. In this study, Y2O3 was uniformly coated on CuCrZr powder by ball milling to form a composite raw material. The samples were prepared using EB-PBF, and the effects of Y2O3 on the microstructure, high-temperature thermal conductivity and mechanical properties of the alloy were investigated. The research results show that the samples with Y2O3 added trigger heterogeneous nucleation at the liquid-solid front, transforming the columnar matrix into equiaxed fine grains. In addition, the in-situ formed Cr2O3 nanoprecipitate was refined, generating a completely coherent interface. Therefore, without sacrificing thermal conductivity, the yield strength increased from 116 MPa to 264 MPa. The thermal conductivity is 328.7 W/(m & sdot;K) at 25 degrees C, and it can still maintain a high thermal conductivity of 283.7 W/(m & sdot;K) at 700 degrees C. This work provides an expandable approach for the preparation of copper alloys with high strength and high thermal conductivity at high temperatures.

Objectives:Osteoporotic bone defect repair remains clinically challenging due to persistent low-grade inflammation, excessive reactive oxygen species (ROS), and dysregulated bone metabolism. Approaches relying solely on osteoclast inhibition are often insufficient, particularly for irregular osteoporotic bone voids. This study aimed to develop a multifunctional microsphere system capable of sequential osteoimmune regulation and bone metabolic remodeling. Methods:Gelatin microspheres grafted with alendronate and loaded with epigallocatechin gallate (Gel@ALN@E) were fabricated via an emulsion-chemical crosslinking method to enable controlled dual-drug release. In vitro evaluations included ROS scavenging, inflammatory modulation, macrophage polarization, osteoclast differentiation, and osteogenic responses of rat bone marrow mesenchymal stem cells. Transcriptomic analysis was conducted to investigate immunoregulatory mechanisms. An osteoporotic rat bone defect model was used for in vivo assessment. Results:Gel@ALN@E effectively reduced oxidative stress and inflammatory responses by promoting macrophage M2 polarization, while concurrently suppressing osteoclastogenesis and restoring bone metabolic balance. This coordinated regulation significantly enhanced osteogenic differentiation. Transcriptomic analysis revealed the downregulation of related inflammatory pathways. In vivo, Gel@ALN@E markedly improved new bone formation, trabecular organisation, and cortical bone healing in osteoporotic defects. Conclusion:This sequential drug release system offers a promising platform for both immunomodulation and bone regeneration in osteoporotic defect repair. The Translational Potential of this Article:The composite engineered microsphere system Gel@ALN@E integrates local immunomodulatory and osteoclast-inhibitory functions to directly address key pathological microenvironmental features of osteoporotic bone defects. This integrative design highlights its comprehensive pro-regenerative capacity and provides support for its translational application in the clinical treatment of irregular osteoporotic bone defects.

The effect of forming temperature on the interfacial bonding mechanism and mechanical properties of Cu/Al composites is systematically investigated via the extrusion-shear process. Within the temperature range of 500-560 degrees C, the interface of Cu/Al composites undergoes a transition from mechanical interlocking to metallurgical bonding. Meanwhile, excessively high temperatures induce the formation of excessive intermetallic compounds (IMCs), leading to the fracture mode of the Cu matrix transforming from quasi-cleavage fracture to brittle fracture, whereas the Al matrix maintains a ductile fracture mode throughout. Overall, 530 degrees C is identified as the optimal forming temperature in this study. At this temperature, the formation of excessive IMCs is suppressed, balancing diffusion and ductility. Additionally, the dynamic recrystallization mechanism of aluminum is activated at 530 degrees C, refining the average grain size to 45.9 mu m. In contrast to the Al matrix, copper exhibits dynamic recovery at all three temperatures investigated.

High-speed steel (HSS) is widely used in cutting tools, hot-rolling rolls, bearings, and cold extrusion dies because of its high hardness, red hardness, wear resistance, and thermal stability. However, severe contact conditions may cause pronounced friction and wear at the interface between HSS and the workpiece material. In this study, graphite (Gr)–CuSn10 composite coatings with different Gr contents were deposited on HSS substrates by atmospheric plasma spraying. The effects of Gr content and applied load on the friction coefficient, wear rate, worn surface morphology, and wear mechanism of the coatings were systematically investigated under controlled laboratory sliding conditions. Increasing Gr content reduced the average friction coefficient from 0.83 for the graphite-free CuSn10 coating to 0.47 for the 7 wt.% Gr coating and 0.42 for the 15 wt.% Gr coating. However, the wear rate first decreased and then increased with increasing Gr content; the 7 wt.% Gr coating showed the lowest wear rate, which was 46% lower than that of the graphite-free coating. The optimized performance of the 7 wt.% Gr coating was attributed to the formation of a graphite-rich lubricating layer while maintaining sufficient continuity and load-bearing capacity of the CuSn10 matrix. In contrast, excessive Gr addition promoted graphite-rich regions and matrix discontinuity, resulting in delamination and reduced wear resistance despite the lower friction coefficient. As the applied load increased from 5 to 30 N, the friction coefficient of the 7 wt.% Gr coating decreased within the investigated load range, whereas the wear volume and adhesive damage increased. These findings indicate that the tribological performance of Gr–CuSn10 composite coatings is governed by the balance between graphite-induced lubrication and matrix integrity, providing guidance for the design of Cu-based solid lubricating coatings for HSS surfaces.

Carbon fibers were functionalized by metal-organic frameworks (MOFs), referred to as MCFs, through chemical self-polymerization and solvothermal reactions, and then combined with polytetrafluoroethylene (PTFE) to construct a hard-soft cross-scale synergistic structure, resulting in the preparation of polyimide (PI) composite coatings. Tribological tests were conducted under different conditions, after which the fundamental role of MCFs and PTFE in modifying the friction-reduction and anti-wear performance of PI was discussed based on in-depth characterization of the composite coatings' worn surface and transfer films formed on the counter steel surface. It was revealed that the MCFs/15PT/PI composite coating exhibited excellent tribological properties, which also exhibited high friction stability and wear resistance across varying loads and sliding speeds. Additionally, the composite coating was found to be potentially applicable for maintenance-free applications due to its excellent long-term tribological performance.

To improve the high-temperature performance of GH5188 cobalt-based superalloy， 10%（volume fraction） TiC particle-reinforced GH5188 composites are fabricated by laser melting deposition （LMD）. The microstructure and tensile properties are investigated， and the interfacial forming mechanism and the cause of the high-temperature performance degradation are discussed. The results show that the composite consists of TiC， （W，Ti）C1-x， and the austenitic γ phase. The submicron-thick （W，Ti）C1-x interfacial layer forms between the TiC particles and the matrix. The interfacial layer originates from the partial dissolution of TiC and the diffusion and substitution of W elements during the laser melting deposition process. At room temperature， the ultimate tensile strength （UTS） of the composite reaches 1198.9 MPa， which is 24.3% higher than that of the matrix alloy （964.3 MPa）. However， at 1000 ℃， the UTS of the composite is 128.7 MPa， which is lower than the 162.5 MPa of the matrix alloy， with a decrease of 20.8%. The degradation in high-temperature strength is mainly due to the consumption of W elements in the matrix by the （W，Ti）C1-x interfacial layer， resulting in decrease in its mass fraction and weakening the solid-solution strengthening and dislocation-pinning effects on the matrix.

Carbon-coated aluminum has emerged as a promising current collector (CC) for lithium batteries, offering significant advantages such as mitigating aluminum foil corrosion, reducing interfacial electron transfer resistance, and enhancing long-term cycling stability and rate performance. In this work, an ultrathin reduced graphene oxide (rGO) coating was fabricated on aluminum foil through a facile binder-free drop-coating and Vitamin C-immersion reduction method. By tuning the GO loading amount, a series of rGO-coated CCs with different coating thicknesses was obtained and evaluated in LiMn2O4 (LMO) batteries under 4.5 V. The results show that electrochemical performance is not determined by coating thickness alone, but by the synergistic effects of coating thickness and defect density. Among samples, the CCs with rGO coating of less than 5 nm thickness exhibit the best rate performance and durability, retaining 85.2% capacity after 500 cycles at 1C (148 mAh·g−1), far surpassing pure Al CCs (73.2%). Post-cycling analyses indicate that the ultrathin rGO coating effectively stabilizes the interfacial environment and mitigates corrosion-related surface degradation during cycling. These findings not only advance our understanding of the role of carbon coatings in mitigating degradation mechanisms but also pave the way for the development of more efficient and durable energy storage systems.

Metallic scaffolds with lightweight, low elastic modulus, and high energy-absorbing capacity are widely utilized in industrial applications but usually require post-heat treatment to enhance their comprehensive mechanical properties. However, it is unclear how to utilize the impact of β-Nb on the surrounding matrix for NiTiNb ternary alloys to achieve strength-ductility-superelasticity enhancement. Here, we prepared rhomboidal dodecahedral NiTiNb porous scaffolds with a porosity of 85.9% by additive manufacturing. Subsequently, annealing treatment was employed to drastically reduce the phase transformation temperatures and expand the thermal hysteresis. Interestingly, the 850°C annealed scaffold exhibited exceeding double compressive strength of the as-built sample, with a remarkable improvement in ductility and superelasticity. From the microstructure perspective, high-temperature annealing caused a further eutectic reaction of the unmelted Nb particles with the NiTi matrix and the transformation of mesh-like β-Nb into diffuse spherical β-Nb particles. The microstructure evolution after deformation indicated that stress-induced martensitic transformation occurred in the matrix away from the NiTi-Nb eutectic region whereas almost no martensite formed nearby β-Nb particles. Atom probe tomography characterization revealed an element diffuse zone in several nanometers surrounding the β-Nb particle, where the substitution of Nb with Ti led to a higher Ni: Ti atomic ratio, lowering transformation temperatures. Molecular dynamics simulations illustrated that β-Nb particles can not only entangle dislocations internally, acting as reinforcements but also hinder the twin growth, contributing to strain hardening. This work elucidates the influence of β-Nb particles on the deformation mechanism of the NiTi-Nb eutectic region through in-depth atomic-scale investigation, which can provide inspiration for the improvement of comprehensive mechanical properties of NiTiNb alloys.

During metallic coating deposition by atmospheric plasma spraying (APS), air entrainment into the plasma jet inevitably leads to oxidation of the molten metallic droplets. The oxides formed in-flight accumulate within the metallic coating, which significantly degrades the performance of the coating compared to the bulk counterpart. It is widely believed that the in-flight oxidation behavior of metal droplets and the state of oxides on their surfaces are critical factors affecting the subsequent spreading behavior and bonding formation of the metal droplet on the substrate surface. In the present work, individual in-flight droplets were collected with liquid N2 to investigate their in-flight oxidation and the oxide state on the droplet surfaces. The effect of in-flight oxidation on the bonding formation of NiCrAlY splats with the superalloy substrate was examined by the focus ion beam (FIB) technique and high-resolution transmission electron microscopy (TEM). Results reveal that the oxides formed during flight within the plasma jet primarily exist in two forms, including small-sized oxide nodules inside the particles and an oxide cap covering the particle surface. SEM examination of splat morphology shows that the high-temperature molten oxide cap is located in the tail of the NiCrAlY metal droplet when the droplet travels through the plasma jet. This oxide distribution pattern results in the metal droplet impacting the substrate first, followed by the deposition of the oxide on the metal splat surface. FIB analysis reveals that the molten oxides deposit on the NiCrAlY splat surfaces without affecting the interfacial bonding at the impact center between splats and substrate. However, these oxides cause entrapment at the periphery of the splats and hinder the bonding between the splats and the substrate. TEM evidence confirms that metallurgical bonding forms at the impact center of the particle due to the absence of oxide film. Chemical bonding is locally achieved at oxide-containing interfaces, whereas delamination dominates most interfacial regions. The effect of high-temperature molten oxides on the bonding mechanism between NiCrAlY splat and substrate is addressed.