中国人民解放军陆军装甲兵学院

Metallic materials are essential for the long-term survival,development,and prosperity of human society,and they play an increas-ingly important role in promoting socio-economic development.Conventional high-temperature alloys generally operate below 1 200 ℃.Howev-er,with the rapid development of the military and aerospace industries,existing alloy systems can no longer fully meet future service require-ments.Current research focuses mainly on increasing their service temperature limits or developing new materials to replace conventional high-temperature alloys.In recent years,high-entropy alloys(HEAs),designed based on the concept of configurational entropy regulation,have at-tracted extensive attention because they can achieve superior comprehensive properties compared with traditional alloy materials.As a classical dual-phase titanium alloy,TC4 titanium alloy has become an important structural material for key components in aerospace and artificial joint implants owing to its excellent specific strength and biocompatibility below 500 ℃.However,its poor wear resistance in high-temperature envi-ronments limits its application scenarios.In contrast,the NbMoTaNiCr refractory high-entropy alloy exhibits better wear resistance at high tem-peratures.Therefore,preparing an NbMoTaNiCr refractory high-entropy alloy coating on TC4 titanium alloy can improve the high-temperature wear resistance of TC4 titanium alloy and expand its application scenarios. At present,studies on the preparation,microstructure,and properties of high-entropy alloy coatings are mostly based on laser additive manufacturing technology.However,because the poor room-temperature plasticity of high-entropy alloys makes wire fabrication difficult,most related studies have used powder materials,and relatively few studies have focused on the preparation of high-entropy alloy coatings by wire arc additive manufacturing.In comparison,wire arc additive manufacturing has the advantages of high deposition efficiency,strong bonding strength,and low cost.Therefore,in this study,a self-designed stranded high-entropy alloy welding wire was used as the raw material,and an NbMoTaNiCr refractory high-entropy alloy coating was prepared on TC4 titanium alloy by TIG rotating arc cladding technology,which is effi-cient,low-cost,and stable in forming quality.The microstructure and properties of the coating were investigated to reveal the structure-proper-ty relationship between its microstructure and wear resistance.This study aimed to provide a key theoretical basis and data support for the engi-neering application of this refractory high-entropy alloy as a wear-resistant component or protective coating. The NbMoTaNiCr refractory high-entropy alloy(RHEA)exhibits excellent mechanical properties and superior wear resistance,showing significant potential for applications in aerospace,nuclear energy,and advanced equipment manufacturing.In this work,a tungsten inert gas(TIG)rotating wire-arc additive manufacturing system was employed to fabricate NbMoTaNiCr RHEA coatings on TC4 titanium alloy sub-strates.The microstructure,hardness,and tribological properties of the deposited layer were systematically investigated.The experimental re-sults revealed that the room-temperaturephase structure of the as-deposited RHEA layer was dominated by a disordered face-centered cubic(FCC)matrix with a small quantity of μ-phase precipitates.The microstructure was characterized by fine and uniformly distributed dendrites,with elemental microsegregation observed between dendritic and inter-dendritic regions.The average microhardness of the alloy layer reached approximately 913 HV.Under identical dry sliding wear test conditions,the deposited RHEA layer exhibited a wear resistance approximately 42 times higher than that of the TC4 titanium alloy substrate.This exceptional performance wasmainly attributed to the synergistic effects of several strengthening mechanisms inherent in the deposited layer.The refined dendritic microstructure significantlyimproved the strength through grain boundary hardening,which conformed to the Hall-Petch relationship.Furthermore,the severe lattice distortion,as a fundamentalcharacteristic of the high-entropy alloy,generated effective solid-solution strengthening and createdconsiderable barriers to dislocation motion.The hard and brittleμ-phase particles belonging to topologically close-packed(TCP)phases further enhanced the wear resistance of the coating.These dis-persed particles effectively inhibited plastic deformation and mitigated abrasive wear during sliding friction.This study verifiedthe feasibility of fabrication high-performance RHEA coatings via the TIG-based wire-arc additive manufacturing and clarified the correlation between the micro-structural characteristics and excellent mechanicaland tribological properties of the coatings.

The stability of micro-droplet ejection and size on-demand are important prerequisites for the direct preparation of bumps in chip packaging. The ejection experiment of SAC305 commercial lead-free solder is carried out by pulsated orifice ejection method （POEM）. The effects of the interaction of parameters such as the pulse waveform， the distance between the transmission rod and the orifice and the orifice， diameter on the ejection stability and particle size during the droplet ejection process are investigated. The surface morphology and microstructure， composition， and phase composition of the solder ball are analyzed. The results show that the stable ejection of droplets and the control of size-on-demand can be realized by coordinating the key process parameters. The deviation between the target particle size and the actual size is within 4%， which can meet the needs for the stable on-demand preparation of bumps. The results of temperature change during droplet solidification show that the cooling rate in the argon atmosphere is much lower than that in the helium atmosphere， so the microstructure is coarser. Combined with the above results， the bumps are directly deposited on the copper plate to form a metallurgical layer， which shows the feasibility of the technology and provides a new way for the direct preparation of bumps.

Objective Broad-area edge-emitting diode lasers have been widely applied in laser pumping, laser ranging, material processing, display technology, and medical fields owing to advantages such as high power, high efficiency, high brightness, compact size, and long lifetime. However, the broad transverse waveguide dimensions of these lasers typically result in significant variations in the optical field under high drive currents, which excites multiple transverse modes. Consequently, the "multilobe" phenomenon occurs in the near-field beam profile, thus severely deteriorating the transverse-beam quality. Additionally, it causes increased far-field divergence angles and reduced brightness, thus limiting their applicability in various fields. Therefore, achieving high power while maintaining high beam quality has become a priority. Methods First, a 100 mu m wide mesa is formed via photolithography and inductively coupled plasma (ICP) etching with an etching depth of 850 nm. Subsequently, side grating structures are etched on both sides of the ridge waveguide using photolithography and wet etching, with an etching depth of 150 nm. A 300-nm-thick SiO2electrical insulation layer is deposited using plasma-enhanced chemical vapor deposition (PECVD). Subsequently, an 80 mu m current injection window is fabricated via ICP etching. Next, a p-side metal contact is deposited, and the wafer substrate is thinned and polished. The n-side metal contact is subsequently deposited, followed by rapid thermal annealing to complete the alloying process. The distance from the etched grating grooves to the mesa is defined as x, and lasers with different values of x (0, 5, 10, 15, and 20 mu m) are fabricated on the same wafer for comparison. After wafer fabrication, cleaving is performed using a dicing machine and a cleaver to separate the wafer into bar-shaped devices. The cavity surfaces are left uncoated and the bars are further cut into single-tube chips. The fabricated chips have a cavity length of 2 mm. Finally, the single-tube chips are bonded to the heat sink, with the p-side facing upward, using a chip mounter. The temperature is controlled using a thermoelectric cooler (TEC). The resolution of the spectrometer used for testing is 0.05 nm, and near-field testing of the device is performed using a 10x magnification objective lens. Results and Discussions As shown in Fig. 4, the single-side output power and voltage characteristics of devices with different x under continuous wave operation at 25 degrees C are presented. First, the voltage performances of different devices are almost identical. However, under different x, the single-sided output powers of the devices exhibit significant differences. As the x increases, the out & hybull; put power of the devices increases as well. The laser spectra at a bias current of 2 A are shown in Fig. 5. When x=20 mu m, the device has a 3 dB bandwidth of 2.223 nm at 2 A bias current, whereas for x=0 mu m, the 3 dB bandwidth is only 1.882 nm, which is 15% lower. Figure 6 shows a comparison of the far-field divergence angles, which is defined by the 95% power, of the lasers at different x. At a current of 1 A, the slow-axis divergence angle is 17.2 degrees when x= 0 mu m, and it increases to 19.9 degrees when x=20 mu m. Figure 7 shows the near-field distributions of lasers with different x at bias currents of 1 A and 2 A. An analysis of these near-field distribution curves reveals that when x=20 mu m, the near field exhibits multiple peaks, thus indicating the presence of significant higher-order mode patterns, and the beam waist width is slightly broader. When x= 0 mu m, the near-field beam waist is slightly narrower and the near-field light field distribution is more concentrated. Conclusions We propose a lateral grating structure and demonstrate its effectiveness in controlling the transverse modes and spectrum of broad-area semiconductor lasers, where a reduced spectral bandwidth is achieved. This structure increases the loss of higher-order modes and enables injection-insensitive transverse divergence without significantly reducing the output power. Owing to its low cost and compatibility with the semiconductor laser manufacturing technology, this structure can be applied to the development of high-power broad-area semiconductor lasers with low divergence and high beam quality.

Fe-based amorphous alloy coatings have emerged as a key area of research in the field of surface engineering due to its high strength,hardness,and exceptional wear and corrosion resistance.This paper provides a comprehensive review of the preparation,performance,and application status of Fe-based amorphous alloy coatings.It also summarizes the fundamental principles of amorphous alloy material design and typical Fe-based amorphous alloy coatings material systems.The focus is on three coating preparation technologies:thermal spraying,cold spraying,and laser cladding.Additionally,it compiles the research progress made in understanding the tribological properties and corrosion resistance of Fe-based amorphous alloy coatings.Furthermore,it briefly outlines the applications of these coatings in military,medical,industrial fields etc.Finally,it is pointed out that in-depth study of amorphous formation,the establishment of specialized material systems while matching the working environment,and the adoption of post-processing or more efficient preparation methods are the development trends for future research work in this field.

The 2022 Beijing Winter Olympics served as a pivotal moment for China, offering a chance to showcase its global image and uplift national pride. A key element of this event was the use of large- and medium-sized snow groomers, which played a crucial role in maintaining optimal conditions for ice and snow sports. These machines not only facilitated the seamless execution of the games but also reflected China’s strength in manufacturing and technology. To meet the growing need for advanced outdoor large- and medium-sized snow groomers, we conducted a thorough review of existing technologies and standards, both locally and abroad. We analyzed challenges such as adapting to different environments, reducing track weight, and ensuring quality control of the body surface. The project systematically addresses the technical challenges in snow groomer propulsion, operating system, overall optimization, manufacturing, testing evaluation, and application. Our goal is to advance the research and development of key components and vehicle technologies to create snow groomers that are highly efficient, reliable, lightweight, and precise. We aim to achieve mass production and establish an effective standard system, reducing China’s reliance of large- and medium-sized snow groomers on foreign imports. Currently, China’s snow groomer industry is still in the starting phase, with a significant gap in design and manufacturing capabilities. Therefore, overcoming the hurdles related to the research and development of key components and vehicle technologies for snow groomers and achieving mass production is an urgent priority. We have conducted research across five levels: demand analysis, key technology research, equipment development, application demonstration, and system construction. This involved focusing on four aspects: promotion system, operation system, whole machine optimization and manufacturing, and testing evaluation. We have explored seven key technologies: high-efficiency static hydraulic drive control for snow road surfaces, lightweight track reliability design, rubber suspension for low-temperature environments, reliability in snow roller vehicles, precise control of snow roller operations in variable environments, lightweight design of snow roller frames and components, and construction of experimental verification technology and indicator system for outdoor large- and medium-sized snow groomers. We have developed the SG400 outdoor large- and medium-sized snow groomer, a model that is efficient, precise, environmentally friendly, and reliable. This snow groomer meets the requirements of international ice and snow events for the track, with performance verified through demonstrations at different ski resorts, such as the 2022 Beijing Winter Olympics, Winter Paralympic Games, and the 14th National Winter Games in 2024. Our efforts resulted in a snow groomer that demonstrates not only high efficiency and reliability but is also lightweight and precise in operation. An effective standard system is now in place, marking a significant shift in China’s snow groomer industry from relying on foreign imports to becoming self-sufficient. This achievement is of great practical significance. Looking ahead, the focus is on advancing snow groomer technology in China by promoting intelligent, green, environmentally friendly, and efficient development.