Samples of 14Ni3Cr3Mo2Mn ultra-high strength steel were successfully fabricated using the dual ultrasonic impact treatment-assisted wire arc additive manufacturing (DUIT-WAAM). The influence mechanism of DUIT on the microstructure evolution and mechanical properties of the WAAM components was systematically investigated. Microstructural test results indicate that the introduction of dual ultrasonic impact significantly altered the solidification behavior of the material. The microstructure of the single-bead single-layer specimen transitioned from coarse, strongly textured columnar dendrites to fine, texture-free equiaxed grains. The grain refinement was most pronounced in the weld toe region, reaching 72.0%. Furthermore, in the WAAM thin-wall components, dual ultrasonic impact effectively fragmented the epitaxially growing dendrites, interrupted the growth of columnar grains across the fusion line, and increased the proportion of high-angle grain boundaries and the dislocation density. Mechanical property test results demonstrate that the introduction of dual ultrasonic impact significantly enhanced the mechanical properties of the as-built thin-wall parts: the average microhardness of the impacted specimens increased from 301.8 HV to 322.1 HV compared to the non-impacted specimens; the horizontal ultimate tensile strength increased from 971.5 MPa to 1165.3 MPa, and the vertical strength increased from 943.5 MPa to 1122.0 MPa. Although the vertical elongation decreased slightly due to interlayer melt pool misalignment, the horizontal elongation was maintained at 11.45%. This study achieved grain refinement and texture weakening in WAAM samples through dual ultrasonic impact, providing new insights for addressing the issues of coarse microstructure and anisotropy in the additive manufacturing of ultra-high strength steels.

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The formation of titanium-iron compounds during the fusion welding of titanium steels continues to pose a significant challenge. In this paper, pure copper filler wire was employed in TIG welding to join TC4 titanium alloy and 304 stainless steel. The solidification behavior of the titanium-steel molten weld interface and the morphological distribution of the brittle phase were controlled by introducing a low-power ultrasonic energy field to assist the welding process. Results indicated that the low-power ultrasonic energy field enhanced the diffusion of joint elements, leading to biased aggregation of brittle phases on the titanium and steel sides, thereby reducing the joint's mechanical properties. The high-frequency vibration produced by the increased ultrasonic power resulted in a slower diffusion of the concentration gradient, creating a more homogeneous distribution of the Ti-Fe brittle phase in the Cu interlayer. This improved the joint properties and results in the middle of the weld consisting mainly of a discontinuous Ti-Fe phases. Additionally, the distribution of the Ti-Cu phase and alpha-(Fe,Cr) phase became more uniform. The high-frequency vibration effectively reduced the residual stresses in the titanium-steel joints, thereby enhancing the overall performance. The tensile strength of the joints reached up to 346 MPa, an increase of 12.7% compared to before ultrasonic vibration was added.

The study examined the impact of peak current and duration on droplet transition, droplet explosion, and spatter during cold metal transfer welding of high-nitrogen austenitic stainless steel wire (0.99 wt.

Silver nanowires (AgNWs) have been widely used in flexible transparent electrodes. Femtosecond laser postprocessing is used to reduce the sheet resistance of AgNW electrodes. However, the melting behavior and welding patterns during femtosecond laser welding are not yet clear. In this article, the light field model, electric field model, and temperature field model of AgNW networks under the action of a femtosecond laser are constructed based on finite element software. By changing the energy density and polarization conditions of the femtosecond laser, the electric fields and power density distribution excited by single and multiple AgNWs networks are simulated. The electron temperature field and lattice temperature field reveal the laws of AgNWs melting and welding under the action of a femtosecond laser: A single AgNW cannot achieve electric field enhancement; an increase in the number of AgNWs at the junctions can strengthen the local electric field enhancement effect. AgNWs aligned as parallel as possible to the laser polarization direction are more susceptible to melting. Altering the laser energy density can significantly change the melting behavior of the AgNW network. Whether the AgNW network will melt on a large scale depends on whether the laser can heat the AgNWs above the melting point at a polarization angle theta of 45 degrees. The time required for an AgNW network to undergo one temperature cycle is 1 ns, which is 1/1000th of the interval between femtosecond laser pulses. Each temperature cycle of the AgNW is an independent event that does not accumulate heat.

Glass, as an amorphous material with excellent optical transparency and chemical stability, plays an irreplaceable role in modern engineering and technology fields such as semiconductor manufacturing and micro-electro-mechanical systems (MEMS). For example, borosilicate glass, with a coefficient of thermal expansion (CTE) that is close to having good thermal shock resistance and chemical stability, can be applied to MEMS packaging and aerospace fields. SiO2 glass exhibits excellent thermal stability, extremely low optical absorption, and high light transmittance, while also possessing strong chemical stability and extremely low dielectric loss. It is widely used in semiconductors, photolithography, and micro-optical devices. However, the stress sensitivity of traditional mechanical joints and the poor weather resistance of adhesive bonding make conventional methods unsuitable for glass joining. Welding technology, with its advantages of high joint strength, structural integrity, and scalability for mass production, has emerged as a key approach for precision glass joining. In the field of glass welding, technologies such as glass brazing, ultrasonic welding, anodic bonding, and laser welding are being widely studied and applied. With the advancement of laser technology, laser welding has emerged as a key solution to overcoming the bottlenecks of conventional processes. This paper, along with the application cases for these technologies, includes an in-depth study of common issues in glass welding, such as residual stress management and interface compatibility design, as well as prospects for the future development of glass welding technology.

Additionally, the mechanical properties of the alloy further decrease with the increase of the hydrogen ion concentration in the hydrogen-charged solution, and the fracture region near the surface shows more obvious brittle fracture characteristics. The precipitated phase, which undergoes a phase transition after hydrogen charging, remains on the surface of the BCC phase during fracture to form a higher and denser raised structure, and a structure distinct from the two phases is also found at the phase boundary. The evolution of hydrogen-induced nanoprecipitated phases leads to a decrease in the overall mechanical properties of the alloy. Additionally, the mechanical properties of the alloy further decrease with the increase of the hydrogen ion concentration in the hydrogen-charged solution, and the fracture region near the surface shows more obvious brittle fracture characteristics. The precipitated phase, which undergoes a phase transition after hydrogen charging, remains on the surface of the BCC phase during fracture to form a higher and denser raised structure, and a structure distinct from the two phases is also found at the phase boundary. The evolution of hydrogen-induced nanoprecipitated phases leads to a decrease in the overall mechanical properties of the alloy.

The mechanical properties and corrosion performance of Al-Zn-Mg alloy through varied flame rectifications was studied based on the intergranular corrosion, exfoliation corrosion experiment. The results showed that the flame rectification accelerated the corrosion susceptibility of Al-Zn-Mg alloy. And the maximum intergranular corrosion depth are detected with the value of 89 mm after three time of flame rectification. The tensile strength of Al-Zn-Mg alloy increased to 383 MPa after one time of flame rectification in 300 °C. Then there is no significant change of tensile strength of Al-Zn-Mg alloy with the increase of flame rectification times. The change of corrosion resistance of Al-Zn-Mg alloy with varied flame rectifications is mainly associated with the transformation of precipitates and grains. There is a notable increase in the precipitation of phases within the grains after one time of flame rectification at 300°C. However, after two times of flame rectification, a phenomenon of "redissolution" of precipitated phases occurs. After three times of flame rectification, small-sized new grains appear at the grain boundaries of the elongated grains within the correction area, which is the result of incomplete recrystallization in the alloy.

Due to the influence of manufacturing errors, welding deformation of ship parts and other factors, interference often occurs due to out-of-tolerance assembly clearance for ship rib plate assembly using the pull-in method. To solve the problem, a clearance control and interference repair method for ship rib plate assembly is proposed. Firstly, the factors causing ship rib assembly errors were analyzed, and an accurate model of the ship rib with manufacturing errors was built based on a 3D scanning point cloud. Secondly, the fit clearances between multiple components during the motion process were calculated based on simulation. Finally, the assembly clearances were redistributed through pose coordination technology to autonomously control the assembly clearance, allocate excess clearances to interference areas and quantitatively complete the subsequent interference processing. The case study results show that the proposed method can achieve quantitative prediction of assembly clearances and generate a precise repair scheme. The interference for ship rib plate assembly is reduced by 50%, and the efficiency is increased by 24%.

All -metal sandwich panels of auxetic honeycomb are usually ultralight and robust but have poor vibration damping. The in -plane auxetic honeycomb sandwich panels (AHSPs) with polyurea-metal laminate (PML) were presented, and its vibration and damping characteristics were studied. The damping characteristic analysis model of the auxetic honeycomb sandwich structure of the PML panel was created by ABAQUS and the model was verified. The frequency/time response curve, natural frequency, mode shapes, and damping loss factor were simulated by the finite element (FE) method, which was then compared with the sandwich plate without a polyurea layer. To investigate potential enhancement processes and examine vibration -damping characteristics, a finite element -modal strain energy (FE-MSE) integrated approach was put forward, taking into account the natural frequency and damping behavior of polyurea. The damping of the PML panel significantly increased due to the viscoelastic energy consumption of the polyurea layer. By reasonably adjusting the thickness and distribution of the polyurea layer, the passive damping ability of sandwich panels can be further enhanced. The frequency and damping loss factor of the AHSPs were able to be successfully improved by raising the thickness of the polyurea layer. The symmetric PML-A laminate was better than the asymmetric structure in vibration reduction, and the damping loss factor can grow from 29% to 40%, with a thickness ratio of 3 3 .

Due to their high load-bearing capacity and excellent energy dissipation properties, metal honeycomb lightweight sandwich panels are commonly utilized as highly efficient weight-saving components in the automotive, aerospace, and military industries. Especially the auxetic honeycomb sandwich panels have higher yield strength, more robust shear modulus, fracture toughness, less fatigue expansion, and higher vibration and energy absorption. In this paper, the ballistic resistance and energy absorption mechanisms of a novel re-entrant auxetic honeycomb (RSH) sandwich panel are investigated. The ballistic limits and energy absorption of the re-entrant star-shaped honeycomb (RSH), star-shaped honeycomb (SSH), and re-entrant star-shaped honeycomb (RH) sandwich panels are compared and analyzed, as well as the deformation mechanism during projectile penetration. The results show that the RSH sandwich panel has the best in-plane ballistic performance among the three types of honeycomb sandwich panels. For the same relative density, the ballistic limit of the RSH sandwich panel is 17.4% and 7.1% higher than that of the SSH and RH sandwich panels respectively. In addition, the effects of different design parameters on the ballistic resistance of RSH sandwich panels are investigated by changing the panel thickness, the relative density of the core layer, the cell angle and the cell size. It can be concluded that increasing the thickness of the face sheet is more effective in improving the ballistic limit (perforation energy) of the RSH with a thinner core layer. However, increasing the relative density of the core layer is more effective in enhancing the ballistic limit (perforation energy) for thicker core layers. Cell size has a significant effect on the ballistic resistance of RSH sandwich panels compared to cell angle, especially at impact velocities close to the ballistic limit.

This paper proposed a mechanical-electrical-hydraulic coupling dynamic modelling method for naval guns coupled with multiple nonlinear factors. The ship's rocking motion equation is derived based on the wave spectrum formula to introduce the influence of random wave excitation into the vibration analysis of naval guns. An efficient gear transmission model of the servo system is developed using a multibody contact-based model to control the computational cost and based on the tooth stiffness theory, the time-varying mesh stiffnesses are considered. The dynamic results show that the ship's rolling motion will have more influence on gun dynamic characteristics than the pitching motion. Though under the control of servo systems, the adverse influence of the ship's rocking motion on cradle motion is basically eliminated. The instantaneous residual disturbances of the cradle increase for the driving torque saturation and the residual disturbances of the cradle will increase gradually with the ship's rocking motion increasing.

To study the multilevel coupled vibration of a naval gun under the foundation motion excitation of the ship, a mechanical-electrical-hydraulic coupled dynamic model of the naval gun including the follow-up systems’ influence was established. The subprogram for calculating the ship foundation motion was written by the harmonic superposition method, and the motion in the 3 and 5-scale sea waves was reconstructed, respectively. Based on the multidisciplinary simulation, the transmission characteristics of the ship’s foundation motion excitation along the naval gun and the influence of the tooth arc arrangement on the stabilization accuracy of the naval gun are analyzed. The results show that: the foundation motion excitation of the ship will aggravate the imbalance of the contact forces at the left and right trunnions of the cradle. A bilateral symmetrical arrangement scheme of the tooth arcs can reduce the contact forces’ imbalance at the trunnions and reduce the adverse influence on the stabilization accuracy of the naval gun. The relevant research provides theoretical support and technical guidance for the structural design or verification of the naval gun.

Al-Li alloys represent a novel category of Al alloys achieved through addition of Li to either pure Al or an Al alloy. This alloy exhibits a low density, exceptional specific strength, outstanding performance at low temperature, and excellent resistance to corrosion. The attainment of high reliability in the joining of Al-Li metals is utmost important for their extensive utilization as structural materials, and the significance of this cannot be overstated. As a pioneering method for solid-state connection, Friction stir welding (FSW) showcasing its revolutionary nature. Notably, its heat input for welding is lower compared to fusion welding, and the welding process does not involve the melting of metallic materials. The present review analyzed and summarized recent advancements in FSW of Al-Li joints. It delved into aspects such as variations in grain size and crystallographic texture in different areas of joints, discrepancies in mechanical properties within various joint regions attributable to different strengthening mechanisms, as well as the corrosion resistance of these joints. Finally, the present study addressed current challenges and outlined future directions for investigation. This included the imperative to enhance the characteristics and quality of Al-Li FSW joints, optimize the FSW process, and develop experimental conditions that closely resemble actual environments. In other words, the primary objective of this extensive review was to furnish a theoretical framework for the prospective advancement of Al-Li joints.

This study investigates the introduction of ultrasonic impact treatment (UIT) during the wire arc additive manufacturing process to refine the microstructure and enhance the properties of 18Ni-300 maraging steel components. It was found that interlayer ultrasonic impact treatment (I-UIT) and synchronous ultrasonic impact treatment (S-UIT) applied to the deposited metal can refine the grains, alter grain growth orientation, and reduce anisotropy. At the top of the formed component, compared to directly deposited specimens, significant grain refinement and the appearance of a 20μm nanocrystalline zone were observed in I-UIT-WAAM samples, while S-UIT-WAAM samples similarly exhibited the effects of ultrasonic impact, with a deeper nanocrystalline zone of 230μm. In the middle of the formed component, due to subsequent remelting and heating effects, the ultrasonic effect was weakened, resulting in the disappearance of the nanocrystalline zone. Compared to I-UIT-WAAM S-UIT-WAAM samples samples, S-UIT-WAAM samples showed better ultrasonic assistance effects due to the ultrasonic impact on the molten pool, with significantly reduced austenite content, average grain size, and texture density. In terms of mechanical properties, for S-UIT-WAAM samples, the horizontal tensile strength was 1401.3 ± 57.6 MPa, and the vertical tensile strength was 1327 ± 9.5 MPa. Compared to directly deposited specimens, the horizontal and vertical tensile strengths of I-UIT-WAAM samples increased by 14.6% and 11.3%, respectively.

Achieving high-strength welding joint of aluminum to steel is a highly pressing and challenging task in the manufacturing industries, and friction stir lap welding (FSLW) has advantages for joining these two metals. To further heighten the strength of dissimilar aluminum and steel metals (Al/steel) FSLW joint, the ultrasonic-assisted FSLW (UAFSLW) process was used, and the upper 2024-T4 aluminum alloy and the lower 304 stainless steel were chosen as research object. The results show that the addition of ultrasound eliminates the micro pores, changes the aluminum-rich intermetallic compounds (IMCs) into the iron-rich IMCs and enhances the micro and macro mechanical interlocking structures along the Al/steel lap interface. Under the rational IMCs layer thickness lower than 1.5 μm, the UAFSLW joint has the failure load higher than the traditional FSLW joint. The maximum failure load of UAFSLW joint reaches 7.06 kN, and the loading capacity of this joint is higher than that of reported Al/steel traditional FSLW joint. The UAFSLW process is an effective way to fabricate the high-strength Al/steel lap joint.

The influences of pre-immersion aeration conditions on the corrosion product films and their erosion-corrosion resistance of 90/10 and 70/30 copper-nickel tubes are investigated. Results show that sealed immersion inhibits the formation of protective films on 90/10 and 70/30 tubes and thus worsens the erosion-corrosion resistance, which is related to the nanosized Mn/O particles near the film/substrate interface. Aerated immersion promotes the formation of protective film on 90/10 copper-nickel tube and improve the film recovery ability of 70/30 copper-nickel tube. Moreover, the features of the corrosion product film with good erosion-corrosion resistance are identified.

Mould bed is crucial for supporting the ship subsection and controlling its deformation during shipbuilding. However, its visualisation and control process intelligence are often inadequate, leading to reduced accuracy and efficiency in ship subsection construction. Aiming at the problem, a three-dimensional (3D) visual monitoring method for the marine intelligent mould bed is proposed based on digital twin, and the overall framework of the management and control system is designed. Meanwhile, a fuzzy PID control principle optimised by the genetic algorithm is proposed to better control the deformation of the ship subsection. On this basis, the verification of the developed system is carried out based on the physical intelligent mould bed, and the 3D visual management and control of the marine intelligent mould bed are realised. It provides a foundation for improving the accuracy and efficiency of ship subsection construction.

Hydrogen diffusion behavior of high-entropy alloy AlCoCrFeNi2.1 was investigated and it was found that the alloy exhibits a low hydrogen diffusion coefficient. Dislocations proliferated greatly in body-centered cubic (BCC) and face-centered cubic (FCC) phases after hydrogenation. Plentiful rhombic net-like morphology appeared on the surface of FCC phase, while abundant nano-scale precipitated phases were found in BCC phases. Subsequent experimental results show that the growth of nano-scale precipitate phases can further delay the hydrogen diffusion and reduce the surface hardness of the alloy. The relationship between the hydrogen-induced evolution caused by hydrogen penetration is strongly correlated with the microstructure and nano-scale precipitate phases in both FCC and BCC phases. Nanophases are found to be responsible for the hydrogen-induced evolution and associated changes in properties of this material.

在附加与焊枪同步运动的超声振动辅助条件下,采用电弧增材制造技术制备2219铝合金单道多层沉积件,并分析其显微组织与力学性能的变化.结果表明:附加超声振动后试样的晶粒明显细化,晶粒粒径在20 μm以下的比例由29.32%提升至46.59%,平均粒径由36.80 μm下降至30.19 μm.同时,在试样的显微组织中出现了大量的亚晶区.经附加超声振动后,试样的显微硬度由79.9HV提升至93.8HV,试样在竖直方向上的拉伸性能得到了一定程度的强化,水平方向上的屈服强度也有所提升,但伸长率显著下降,这可能与拉伸件中存在的缺陷相关.