With the growing demand for high-performance thermal management devices, achieving efficient and reliable joining between 3D-printed SiC-reinforced Ti6Al4V composite (3DP-SiC/TC4) and SiC ceramic presents a critical challenge. To enhance the interfacial thermal conductivity, femtosecond laser treatment (FLT) was applied to the SiC ceramic, aiming to construct a uniform striated microstructure. AgCuTi braze was employed to join 3DP-SiC/TC4 with femtosecond laser-treated SiC ceramic (FLT-SiC). The interfacial reaction mechanisms, microstructural evolution, and thermomechanical property optimization were systematically investigated. Based on a series-parallel thermal resistance model, it was revealed that the FLT significantly reduce interfacial thermal resistance by increasing the effective contact area and promoting metallurgical joining. The FLT influences the synergistic effect between geometric morphology and chemical joining. At 0.63 W, a positive synergy between geometric (gain factor ξgeo = 1.083) and interfacial chemical (κchem = 1.087) contributions was achieved. The brazing temperature regulated the extent of interfacial reactions, with 850 ℃ yielding a dense microstructure and optimal properties. The optimal parameters were identified as a laser fluence of 0.63 J/cm2 and a brazing condition of 850 ℃ for 10 min. Under these conditions, the joint exhibited a shear strength of 46.5 ± 2.4 MPa and a thermal conductivity of 24.6 W·m-1·K-1 at 600 ℃. This study provides a novel approach for joining dissimilar materials in thermal management applications, leading to a significant enhancement in the thermal and mechanical performance of the joint.

Ceramic-reinforced aluminum matrix composites possess exceptional properties, which makes them promising candidates for a wide range of applications. However, the brittle Al4C3 phases, which can severely deteriorate the properties of the joint, are often formed in the joint obtained using conventional fusion welding techniques. In this study, an ultrafast laser welding approach is adopted for the first time to join aluminum matrix composites reinforced with 45 vol.% SiC particles. The achieved joints appear to be sound, free from macroscopic defects, and the four-point bending strength of the joint can reach 321 MPa. The effects of laser power and welding speed on the microstructure and mechanical properties are systematically examined. Comprehensive characterization reveals that, unlike conventional laser welding, no brittle and hydrolyzable Al4C3 phase is detected in the welding seam. Instead, the ultrafast laser irradiation promotes the decomposition of SiC particles, which subsequently react with molten aluminum to form nanoscale Al4SiC4 phases. These precipitates are uniformly dispersed throughout the matrix, thus enhancing the joint performance.

Niobium alloy and nickel-based superalloy exhibit high strength and remarkable corrosion resistance, joining them to fabricate composite structures could help to realize their potential. Nevertheless, research attention devoted to the joining of niobium alloy with nickel-based superalloy remains scarce. This study investigates direct diffusion bonding of these two materials. The microstructure of the joint is characterized in detail, with the typical joint microstructure being identified as GH4099 / (Ni, Cr)ss + Ni3Nb + Cr2Nb / Ni3Nb / Ni6Nb7 / Nb alloy. With holding time fixed at 60min and diffusion pressure maintained at 15MPa, the effects of diffusion bonding temperature on the microstructure and mechanical properties of joints are examined within the range of 900-1150 ℃. An increase in bonding temperature results in the formation of different intermetallic compounds within the joint. The primary cause of joint fracture is the presence of Cr2Nb and Ni6Nb7. The tensile strength of the joint initially increases and then decreases with increasing temperature, reaching a maximum value of 204MPa. This work expands the range of methods for joining niobium alloys to nickel-based superalloys, enabling bonding without the introduction of additional elements.

This study investigates the high-temperature oxidation behavior in both air and in steam of the SiC joint obtained using FeCoCrNiCu high-entropy alloys via ultrafast high-temperature joining (UHJ). In air, the oxidation of the joints follows a diffusion-controlled parabolic rule at 1000 degrees C, and the high-temperature shear strength of the joint reaches up to 47 MPa, showing a surprising increase by approximately 74 % after oxidation. During the oxidation process, segregated Cr inside the brazing seam center diffuses to regions of high oxygen partial pressure, forming Cr2O3. The formation and volatilization of Cr2O3 is found to play a crucial role in the microstructural evolution of the joint during steam oxidation. The oxidation kinetics in steam are opposite follows the reaction-controlled linear rule, with the oxidation rate of k(l) = 8.68 x 10(-9) m/s. The volatilization of CrO2(OH)(2)(g) leads to the formation of interconnected crack-hole network in the joint, preventing oxides from filling the voids in time and allowing steam to penetrate rapidly.

In this paper, the ultrafast joining of SiC is achieved using Kovar alloy via flash brazing within 15 s. The 4J33 alloy exhibits good wettability on SiC, and the contact angle is 37 degrees at 1220 degrees C. Moreover, during the joining process, Fe and Ni react with SiC to form Ni3Si2, FeSi, and amorphous carbon at the interface. The experimental results show that the joint obtains the best mechanical properties when the current is 12.5 A and the energization time is 15 s. The maximum shear strength of the joint reaches 51 MPa at room temperature, and 38 MPa at 1000 degrees C. In addition, the interface temperature was measured by R-type thermocouple in this experiment. The interface temperature rises from 400 degrees C to 1686 degrees C at the flash moment due to the Joule heating effect. The flash period is only 0.5 s, so the heating rate is as high as about 2400 degrees C/s. In the flash moment, the changes of voltage, current and power are in good agreement with the temperature changes. The voltage peaks at 150 V, then rapidly drops to a steady 13 V, while the current surges to 16 A before quickly settling at 12.5 A. This study significantly enhances the joining efficiency of SiC ceramics and expands the application of Kovar alloy as a new hightemperature filler.

The development of efficient thermal management systems urgently requires reliable joining between 3D-printed SiC-reinforced Ti6Al4V composites (3DP-SiC/TC4) and SiC ceramics. This study comprehensively investigates the microstructure, physical properties and wettability of 3DP-SiC/TC4 fabricated by electron beam melting (EBM). Compared with original TC4, 3DP-SiC/TC4 exhibits a lower coefficient of thermal expansion (8.4 & times; 10(-6)& centerdot;K-1) and a higher thermal conductivity (11.647 W & centerdot;m(-1)& centerdot;K-1). High-quality brazed joints are achieved between 3DP-SiC/TC4 and SiC ceramics using AgCuTi braze. Microstructural evolution, mechanical properties and thermal characteristics are systematically investigated. A layered reaction zone preferentially forms at SiC interfaces, consisting of TiC and Ti5Si3 with a total thickness of similar to 1.0 mu m. The central region of the joint develops a mixed microstructure of Ag(s,s) and Ti-Cu intermetallic compounds, while graded Ti-Cu diffusion zones form on the 3DP-SiC/TC4 side. The heat transfer analysis demonstrates that brazing effectively reduces the interfacial thermal resistance by filling the air gaps. The optimal brazing temperature is 850 degrees C, achieving joints with the shear strength of 39.5 +/- 1.0 MPa and the thermal conductivity of 21.6 W & centerdot;m(-1)& centerdot;K-1 (tested at 600 degrees C), representing 57% and 56% improvements over original TC4 joints respectively. This research provides innovative material joining solutions for lightweight aerospace thermal management system design.

Residual stress is a critical issue in ceramic/metal composite structure joints, yet reports on residual stresses in ceramic/phase-transforming metal joints remain scarce. In this study, the 2D residual stress distribution in a PCBN ceramic and M42 high-speed steel brazed joint is revealed for the first time using synchrotron XRD. The joint comprises a PCBN ceramic, a CuNi interlayer, and M42 steel. Notably, an abnormal residual stress distribution, with tensile stress present at both the surface and interface of the ceramic, is observed for the first time. The residual tensile stress near the ceramic interface exceeds 1000 MPa, and joint fracture occurs in the region of maximum tensile stress at the ceramic interface. Finite element analysis indicates that shrinkage of the CuNi layer dominates in joints formed below the phase transition temperature, resulting solely in residual compressive stress at the ceramic interface. In contrast, high-temperature XRD analysis and thermal expansion coefficient measurements confirm that the volume expansion caused by the phase transformation of M42 steel is a key factor contributing to the tensile stress at the ceramic interface.

Thanks to its excellent thermal conductivity, copper material is widely used in industrial plate heat exchangers within the nuclear energy and power generation industries. However, due to its relatively poor mechanical strength, the copper components requires surfaces strengthening. One viable approach is to form a fine-grained layer with enhanced mechanical properties through surface mechanical treatment. However, the fine-grained structures are prone to grain coarsening and even abnormal grain growth (AGG), leading to rapid deterioration of strengthening. In this study, we successfully implemented friction stir surface compositing (FSSC) on pure copper with hybrid micro/nano-TiC particles under ultralow heat-input, achieving a low processing peak temperature of 367.3 degrees C. The TiC particles provided effective Zener pinning on dislocation migration and grain boundary coalescence, resulting in a strengthened fine-grained surface with remarkable microstructural and mechanical thermal stability. After 700 degrees C-30min thermal exposure, FSSC specimens maintained 83 HV surface hardness (50.9 % increase over base material) and 203.2 MPa tensile strength (54.5 % enhancement). Notably, the size of TiC particles performed a temperature-adaptive relationship with the thermal stability of the FSSCprocessed surface. At intermediate temperatures (400 degrees C), 40 nm TiC particles provided superior thermal stable effect, while at high temperatures (700 degrees C), 5 mu m TiC particles exhibited better thermal stable improvement. Furthermore, in addition to fine grain strengthening and dislocation strengthening mechanisms, the FSSC specimens benefited from Orowan strengthening and twinning-induced plasticity (TWIP) effects induced by TiC particles, achieving a strength-ductility synergy compared to the FSSP. This study provides a practical example for surface strengthening of copper alloys in high-temperature service environments.

Fine-grained materials have demonstrated superior properties such as high strength and hardness, making them suitable for surface strengthening of pure metals. However, the main drawback of fine-grained materials hindering their further application is that fine microstructures are vulnerable to high temperatures. To overcome this challenge, we developed a fine-grained copper composite surface with outstanding thermal stability via nano-TiC particles reinforced friction stir surface processing (TiCp/FSSP). The composite surface retained a finegrained microstructure after annealing at 700 degrees C for 30 min due to the dual mechanisms of nano-TiC mediated Zener pinning and nanoparticle-dislocation-twin interactions. Notably, compared to the FSSP method which enhances tensile strength at the expense of elongation, the TiCp/FSSP elevates the tensile strength of the copper alloy to 294.1 MPa while maintaining a high elongation of 41.5 % attributed to the dislocation pinning and twin-induced plasticity of nano-TiC particles, achieving a strength-ductility synergistic optimization.

The direct welding of alumina and zirconia ceramics by ultrashort pulse laser is presented for the first time. Compared to traditional dissimilar ceramic joining techniques such as brazing and diffusion welding, this method shows various advantages, including operation at room-temperature, higher welding efficiency, and negligible impact on base materials. The joint microstructure consists of a combination of Al2O3 and ZrO2 phases, without new phases detected. By adjusting the laser focal point position, the phase content within joint is effectively regulated, successfully preventing crack formation in alumina substrate. The influence of laser power and welding speed on joint morphology and mechanical property is fully investigated. The highest four-point bending strength of 365.5 MPa and shear strength of 33.4 MPa are achieved. After experiencing thermal cycling test at 1000 degrees C, the joint strength and microstructure does not exhibit significant changes, demonstrating the excellent high-temperature durability of the sample.

Ultrashort pulse laser (USPL) with its excellent properties of ultrashort pulse width and extremely high peak power is widely applied in precision machining, microfabrication, and biomedicine. In recent years, there is a growing trend in using USPL in the field of welding. This emerging welding technology is primarily applied to the welding of transparent materials. By focusing USPL at the welding interface, laser energy transfers to substrates within a narrow area through the nonlinear absorption process, accompanied with large amount of heat release to achieve the melting and bonding. Due to the extremely short pulse width and limited energy input, thermal diffusion around the joint is minimal, resulting in the diminished welding region, lower thermal stress, and enhanced welding precision. This method holds significant promise for welding samples with a large coefficient of thermal expansion (CTE) difference. In this review, the welding of transparent materials is first introduced, including the welding process, mechanism, and process optimization. Following this, the welding of transparent materials‐opaque materials and opaque materials‐opaque materials are described. The current progress in the applications of USPL welding is then presented. Finally, the development prospects of USPL welding technology are summarized and discussed.

To address the challenges of protonic ceramic fuel cell (PCFC) stack sealing, a TiO2-containing alkaline silicate glass, named STKN, was utilized to seal the BaZr0.1Ce0.7Y0.1Yb0.1O3-s (BZCYYb) electrolyte and Crofer 22 H stainless steel, achieving a sufficient bonding. The formation of the BaTiSi2O7 reaction layer at the BZCYYb interface is the key to realizing effective joining. Elevating the joining temperature results in a thicker BaTiSi2O7 reaction layer and a concomitant loss of the sealant. The optimal sealing parameter is determined to be 775 degrees C for 30 min, yielding a maximum shear strength of 20 MPa. After aging in both oxidizing and reducing atmospheres at 600 degrees C for 300 h, the microstructure of the joint remained stable, suggesting excellent potential for service stability of the joint.

The direct welding of alumina ceramic and titanium using ultrashort pulse laser was successfully achieved for the first time. Benefitting from the extremely high peak power of ultrashort pulse laser, ceramics can be melted at a very low laser power. The emerging welding method was conducted at room-temperature without the need for preheating. Within the joint, a combination of Ti and Al elements was observed. A newly formed TiO2 phase was identified at the Al2O3/welding seam interface. Under the optimal welding parameters (welding speed: 0.8 mm/s, laser power: 19.52 W), the joint achieved a maximum four-point bending strength of approximately 134.9 MPa. This study proposed a new methodology for butt welding of ceramics and metals and shows a much higher efficiency than the commonly used ceramic-metal joining approaches such as brazing and diffusion bonding.

The structural adhesive bonding of aluminum is widely used in the aircraft and automotive industries. The surface preparation of aluminum prior to adhesive bonding plays a significant role in improving the bonding strength. Surface cleanliness, surface roughness, and surface chemistry can be controlled, primarily, by proper surface treatment methods. In this study, the effect of varying the chemical treatment period on the adhesive bonding characteristics was investigated. An epoxy adhesive was used to join the treated surfaces, and the bond strengths were evaluated via single lap-shear (SLS) tests in pristine, as well as degraded, conditions. The surface morphology, chemistry, and corrosion properties of the surfaces with chemical treatments were characterized using various surface analytical tools, such as scanning electron microscopy, an energy dispersive spectrometer (SEM/EDX), and an electrochemical workstation. Excellent adhesion characteristics, with the complete cohesive failure of the adhesive, were encountered on the surfaces of the H2O2-treated samples. The H2O2-treated samples exhibited the highest initial bond strength, reaching 22.5 ± 0.5 MPa, and showed a decrease of only 10% (to 18.1 ± 0.2 MPa) after aging under extreme humidity and temperature conditions (70 °C and 100% R.H. for 4 weeks). The chemical treatment reported in this work is a very simple method to produce durable joints.

To enhance the ablation resistance of carbon-reinforced carbon aerogel (C/CA) composites, a SiC/ZrC-SiC coating was applied using slurry brushing and gaseous silicon infiltration techniques. The samples were exposed to an oxyacetylene flame at temperatures exceeding 2000 degrees C for 60 s, after which the peak front-side temperature of the coated C/CA was 288 degrees C lower than that of pure C/CA. The linear ablation rate of the coated C/CA (1.72 f 0.08 mu m/s) decreased by 89.7% compared to that of pure C/CA (16.4 f 0.08 mu m/s). The reduction in the front- side temperature was attributed to the high emissivity of the SiC coating and the evaporation of SiO2 during ablation. Moreover, due to its low oxygen permeability, the dense SiO2-ZrO2 layer prevented the inner coating and matrix from further oxidation. In addition, the introduction of phenolic resin nanoparticles within the C/CA matrix limited heat conduction, resulting in a peak back-side temperature of only 91 degrees C for the 10-mm-thick sample.

Improving the wear and corrosion performances of widely employed copper and its alloy components can effectively extend their service life. In this study, a novel copper surface modification method based on the friction stir surface processing (FSSP) technique was achieved. Subject to FSSP with pinless tool and low heat-input process parameters (including a minimal axis tilt and extremely low rotational speed), the modified copper surface exhibited enhancement rates of 34.25 % in hardness and 44.76 % in tensile strength, and improved high wear and corrosion resistance characteristics. The research suggests that the primary reasons for the enhanced surface properties are the grain refinement strengthening effect and the rapid formation of a passive film. Additionally, the ultra-low heat input resulted in the preservation of numerous dislocation tangles and incomplete dynamic recrystallization in the modified region, which represented a microstructural evolution mechanism distinct from the traditional friction stir processing. This work provides a reference for a low-energy-consumption and easily achievable approach for enhancing the surface properties of metals.

In this work, the brazing of Zircaloy-4 (Zr-4) to Ti3AlC2 ceramic was investigated using a Ti-13Zr-21Cu-9Ni (wt.%) amorphous alloy at 930 degrees C with a holding time of 5-60 min. The typical multilayer structure of the joint was carefully characterized as Ti3AlC2/ZrC/Zr [Ti](ss) + [Zr(Ti)](2) [Cu(Ni)]/Zr [Ti](ss)/Zr-4. Ti3AlC2 was decomposed into TiCx due to the de-intercalation of Al, and Zr-4 dissolved into the molten amorphous TiZrCuNi fillers to form a Zr-based alloy which reacted with TiCx to form a ZrC particle layer on the Ti3AlC2 side. The microstructures and mechanical properties of the brazed joint were significantly influenced by dwell time, and the underlying evolution mechanisms were addressed based on the considerations of mutual dissolution, diffusion, and reaction among Ti3AlC2, Zr-4, and molten amorphous alloys. With the extension of holding time, the amount of [Zr(Ti)](2) [Cu(Ni)] in the brazed joints decreased gradually, while the ZrC layer thickened with (Ti, Zr)(ss) formed around the ZrC particles. The maximum shear strength of the joint, with an average strength of 187 +/- 34 MPa, was achieved by brazing at 930 degrees C for 5 min. A detailed fracture analysis was conducted to determine the failure mechanism. This work provides a reference for brazing other MAX phase materials and alloys.

The resin infiltration concept is one of the most widely used minimally invasive restorative techniques in restorative dentistry with the most outstanding therapeutic effect, and it is also one of the key research directions in restorative dentistry. “Infiltration resin” is the specialty restorative material for the technology, which is the key factor to success. The specialized restorative material is commonly known as “infiltrant/infiltration resins” “resins infiltrant” “infiltrant” or “resins,” which will be consistently referred to as “infiltration resins” throughout the article. The paper aims to provide a comprehensive overview of infiltration resins by introducing the development of their therapeutic mechanisms, basic components, current challenges, and future trends, Based on existing literature, we analyze and compare how changes in the base monomer's structure and ratio affect the effectiveness of infiltration resins, from the material's structure-effective relationship. After compiling the information, the existing solution strategies have been listed to offer substantial support and guidance for future research endeavors.

The time consumption of ceramic joining methods has hindered the widespread application of ceramic components in the industry. The recently proposed ceramic joining approach via ultrashort pulse laser welding could be a feasible solution to this problem. Herein, we optimised the welding parameters and conducted a comprehensively characterisation of the joint microstructures and fracture morphology. The achieved four-point bending strength reached approximately 60% of that of the base material. The welding mechanism was hypothesised from the perspective of nonlinear absorption of the ultrashort pulse laser by the alumina ceramic. These results are expected to provide an in-depth understanding of the emerging technology.