This study demonstrated that the optimized AlTiFeCrMoSi0.2 high-entropy alloy (HEA) coating can significantly improve the corrosion resistance of the T91 steel in high-temperature liquid lead-bismuth eutectic (LBE) environment. Compared with the commercial T91 steel, the thickness of oxide scale on the HEA-coated steel after 1000 h of corrosion in oxygen-saturated and low-oxygen LBE environment was reduced by factors of 5.7 and 13.11, respectively. Under saturated oxygen conditions, the oxide scale on T91 steel was dominated by Fe3O4 and FeCr2O4 spinel phases. In contrast, the coating system developed additional protective layers of TiO2 and continuous Al2O3.Under low oxygen environments, the oxide structure on T91 steel transitioned to a mixture of Cr2O3 and FeCr2O4, while the coating consistently formed TiO2 and continuous Al2O3 layers. The oxide layer of the coating effectively prevented the penetration of lead and bismuth, thereby suppressing the occurrence of localized dissolution corrosion. Theoretical calculations confirmed the critical roles of TiO2 and Al2O3 in enhancing the coating's resistance to liquid LBE corrosion. This study provides new insights into the development of LBE-corrosion-resistant approaches.

This study investigates the hydrogen embrittlement susceptibility of laser melting deposition (LMD)-produced Ti-6Al-4V alloy with different build orientations (0°, 45°, 90°) through electrochemical hydrogen charging, slow strain rate testing, and microstructural characterization. Ti-6Al-4V alloys are widely used in marine and offshore engineering, where cathodic protection and corrosion reactions can generate hydrogen, leading to hydrogen ingress and potential embrittlement. Results show that prolonged hydrogen charging induces hydride formation, α-phase fragmentation, and β-phase dissolution, significantly degrading corrosion resistance and mechanical properties. Hydrogen embrittlement susceptibility exhibits notable anisotropy: elongation reductions for 0°, 45°, and 90° specimens are 40.1%, 40.8%, and 29.4%, respectively. The relatively superior resistance observed in the 90° orientation may be associated with its single-layer structure and more uniform dimple distribution. In contrast, the multilayer interfaces in other orientations are likely to serve as preferential sites for hydrogen accumulation, which may contribute to the increased embrittlement susceptibility. This research reveals the failure mechanism of LMD Ti-6Al-4V in hydrogen environments and supports its application in marine engineering.

The Ti-6Al-4 V alloy produced by laser powder bed fusion (LPBF) is one of the most typical titanium (Ti) alloys, combining the characteristics of alpha-Ti and beta-Ti. Due to its low density, high strength, good toughness, and biocompatibility, it is widely used in fields such as aerospace, high-speed trains, and medical implants. However, its specific microstructure is sensitive to hydrogen absorption and embrittlement, which limits its broader application. This paper investigates the effects of doped graphene nanoflakes (GNFs) on the microstructure and hydrogen embrittlement (HE) resistance of LPBF-formed titanium matrix composites (TMCs) through microscopic characterization and slow strain rate tensile testing with electrochemical hydrogen pre-charging. The results indicate that the presence of hydrogen atoms adversely affects both the strength and plasticity of the composites with varying graphene content, with increased sensitivity to HE as the graphene content rises. The strength loss rates for composites with 0 wt%, 0.1 wt%, and 0.2 wt% GNFs are 7.29 %, 4.84 %, and 19.23 %, respectively, while the plasticity loss rates are 51.70 %, 59.91 %, and 60.57 %. The fracture mode is primarily a mixed ductile-brittle fracture, with the crack initiation and propagation mechanisms transitioning from trans- granular fracture to intergranular fracture. These findings provide a theoretical basis and technical support for the engineering application of LPBF-formed TMCs in hydrogen-rich service environments.

High-entropy alloys (HEAs) have garnered significant global interest due to their outstanding properties. This study investigates the structural stability and mechanical properties of FeCoCrNiMox (x = 0, 0.4, 0.5, 0.8, 1.3) HEAs using a first-principles approach coupled with the special quasi-random structure (SQS) method. Of the alloys examined, all except FeCoCrNiMo1.3 were found to be thermodynamically and dynamically stable. Elasticity calculations revealed that molybdenum improves the ductility and anisotropy of the alloys, though with a slight decrease in strength and stiffness, as confirmed by electronic structure analysis. Defect-free FeCoCrNiMo0.5 HEAs coatings were then prepared using laser cladding and characterized for their microstructure and hardness. The coating exhibited a transition from columnar crystals at the bottom to equiaxed crystals at the surface, forming a honeycomb-like structure. Inside the crystal cells, high-density dislocations and σ-phase were observed. Elasticity calculations of the σ-phase confirmed its high hardness, low ductility, and classification as a brittle, hard phase.

This study investigated the effect of pre-deformation on the corrosion fatigue crack propagation (CFCG) of Al-Mg-Zn alloy in a corrosive environment. Tensile tests at different pre-deformation levels and molecular dynamics simulations analyzed changes in dislocation density. Corrosion fatigue experiments were conducted in a 3.5% NaCl solution at room temperature, and crack propagation morphology was characterized using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that tensile strength increased by 2.63% and 10.00% for 5% and 10% pre-deformation, respectively. The crack propagation threshold values were L2 (6.36 MPa·m1/2) > L0 (6.05 MPa·m1/2) > L1 (5.13 MPa·m1/2), attributed to increased dislocation density and material strength. At 5% pre-deformation, dislocation pile-ups created stress concentrations that facilitated crack propagation. In contrast, the non-uniform dislocation distribution at 10% pre-deformation enhanced both material strength and resistance to crack growth.

Life prediction significantly influences the reliability of LED light sources. While high-power LED light sources theoretically offer a lifespan of up to 100,000 h, irreversible damage to components leads to light failure, substantially reducing their actual lifespan. Consequently, accurate life prediction is pivotal for manufacturers to cut costs and enhance economic efficiency. This necessity aligns with the interests of communities, governments, and consumers. Currently, the most extensively employed prediction methods are based on traditional physical models and data-driven approaches. The focal point of current research lies in realizing model fusion, presenting both a hotspot and a challenge. To elucidate the relationships, advantages, and disadvantages of different algorithms and establish the groundwork for LED life prediction algorithm development, this paper first introduces material properties and the light decay model of high-power LED light sources. Subsequently, it discusses the principles and methods of the physical model concerning light source reliability. The paper also presents a review and comparison of recent domestic and foreign light source life prediction models. Finally, it provides insights into the expected future development trends in life prediction.

介绍了国内外对于磨浆机磨盘间隙测量的研究现状,以及磨浆机磨盘间隙在线测量的改进方法,进一步探讨了电涡流传感器在磨浆机上齿盘边界特性、齿盘变转速响应特性、进退盘响应特性、齿盘的静动态响应性能、输出特性等最佳特性曲线拟合方程.优化了电涡流传感器结合超声波测厚仪对磨浆机磨盘间隙的实时在线测量方案.传感器安装与磨片边缘的距离大于2 mm、动盘外缘线速度大于360 m/min时,电压值稳定,进退盘响应及静动态输出特性变化总体趋于一致,最佳特性拟合曲线方程线性系数大于0.99.

研究了Ni含量对Sn-8Sb-4Cu-xNi(x=0,0.5,1和2,质量分数)钎料熔点和微观组织的影响,用Sn-8Sb-4Cu-xNi钎料对304不锈钢进行钎焊连接,分析了接头的界面组织与剪切性能.结果表明,添加不同含量的Ni后,Sn-8Sb-4Cu-xNi均为近共晶钎料,其熔点约为245℃;Sn-8Sb-4Cu钎料组织由α相基体、Sb2Sn3+Cu6Sn5+Sn复合相和Cu6(Sn,Sb)5相组成.添加Ni元素后,钎料中块状Cu6(Sn,Sb)5转变为细小、均匀分布的(Cu,Ni)6(Sn,Sb)5.当Ni含量小于1％时,随Ni含量的增加,钎料中的复合相和(Cu,Ni)6(Sn,Sb)5相均增加;当Ni含量为2％时,钎料中的复合相和(Cu,Ni)6(Sn,Sb)5相均减少,但(Cu,Ni)6(Sn,Sb)5相中Ni含量增加至与Cu相当;Sn-8Sb-4Cu-xNi/304钎焊界面均形成了一层厚度约1.5μm的扩散反应层,EDS分析显示,该层为FeSn2化合物.钎缝中全部为Cu6Sn5型化合物,未见Sn-Sb型化合物.Ni元素的添加,提高了304/Sn-8Sb-4Cu-xNi/304钎焊接头的抗剪强度,当Ni含量为0.5％时,接头抗剪强度最大,为67 MPa,与不含Ni钎料相比提高了60％.所有接头的断裂位置均位于钎缝.

In this paper, the diameter of 1.2mm and 1.6mm welding wires were used to carry out high-frequency pulse MAG butt welding process test on S355J2W+N weathering steel. The analysis of the microstructure characteristics of the welded joints under the two working conditions shows that there is little difference and both are ideal. There were more acculate ferrite (AF), less pearlite (P) and bainite (BG), and no larger Weisserite structure and less ferrite side-plate (FSP) structure. The weld is well formed, weld defects such as gas pores and cracks are not found. The impact test showed that the impact energy Akv (-40 °C) of the welded joint at -40 °C was higher than the specified minimum impact energy of 27 J. Compared with the 1.2mm welding wire, the impact energy of the 1.6mm welding wire is lower. Tensile test results show that the fracture occurs at the base metal position. and the fracture height is uneven, forming an angle of 45° with the tensile stress direction, which is a ductile fracture. When the bending angle of the butt joint samples reaches 180°, no cracks are both found on the tensile surface, and the plastic index of the welded joint samples is qualified and has good bending performance.

针对大型复杂结构件几何参量在线精密测量的技术难题,本文开展了基于多轴联动激光扫描和结构光三目视觉摄影的尺寸测量技术研究;通过结构方案设计、算法研究、软件开发及系统搭建,研制了针对不同测量对象的多套非接触式几何尺寸测量系统.测试校准结果表明,激光扫描测量系统在15 m距离的测量不确定度为2.656 mm,结构光三目视觉测量系统在7 m距离的测量结果不确定度为1.552 mm,均满足大型结构件的测量范围及精度要求.在此基础上,本文采用两种类型的测量系统同时对生产现场大型热态锻件外圆直径参数进行在线测量,重复测量误差均小于士4 mm,测量结果表现出良好的一致性.研究结果为大型结构件表面和内部几何尺寸的高精度在线测量提供了有效的技术方法和装备.

A low-carbon bainitic steel serving for the high-speed train was jointed with the laser–arc hybrid welding, and the low-temperature (−40 °C) impact toughness of the joint was evaluated. The results showed that the microstructure of each micro-zone of the welded joint was mainly bainite, but the morphology and size were quite different. The average grain size of the weld material (WM) was 1.69 μm, which was 19

根据声弹性原理和胡克定律推导了纵波法和横纵波法的螺栓轴向应力测量公式,探究了纵波法和横纵波法对温度变化的敏感性差异,推导了横纵波法的温度修正模型,并通过试验验证了该模型的精度.结果表明,相比纵波法,横纵波法受温度影响较小,纵波法对温度变化的敏感性约为横纵波法的 2 倍.

A quasi-steady-state laser-GMAW hybrid welding simulation method was developed. The comprehensive effects of buoyancy, thermal capillary force, electromagnetic force and arc shear force were considered in the model, thus the temperature and flow fields characteristics of molten pool were obtained. At the same time, the heat source motion was realized based on the deformed geometry (DG) approach. The model can be applied to laser welding processes with different joint configurations or moving paths.

针对高浓度磨浆机实时测距的迫切需求,为模拟真实工作环境,对磨浆机进行了模型搭建,探究各因素对电涡流位移传感器输入、输出特性的影响,并对定磨片不同磨损程度下传感器的输出结果进行线性拟合.结果表明:动磨片转速基本不影响输出结果;加上定磨片后输出值降低1/2,定磨片磨损程度越深,输出值越大;加水隔离套基本不影响输出值;线性拟合相关系数大于0.99,传感器的线性度较好,能够准确测量磨浆机动、定磨片的工作间隙;由线性拟合斜率可以判断磨片的磨损情况.该传感器能达到实时监控的目的.

A new kind of low-carbon bainite steel with excellent strength and toughness was developed, serving as the bogie of the next-generation high-speed train. However, the softening of the heat-affected zone (HAZ) in laser-arc hybrid welding (LAHW) needs to be overcome. In this study, the effect of the cooling rate of the LAHW process on the microstructure and mechanical properties in the HAZ was explored via thermal simulation. The results showed that with increased cooling rate, the grain size increased, the content of lath martensite decreased, and the lath bainite gradually changed to a granular shape in the thermal simulation specimen. With the decrease in the cooling rate, i.e., with the increase of t8/5, the strength–toughness matching of the material showed a downward trend. The thermal simulation specimen with a t8/5 of 6~8 s had higher strength and good toughness, which can be considered a potential welding parameter reference. The content of martensitic austenite (M-A) constituents was the main factor that determined the strength and toughness of the joint. During the tensile test, the axial force caused the material to tighten, and the transverse stress as obvious in the part of the M-A constituents that are prone to microcracks and many defects, resulting in cracks, paths, and multi-component layers in the center. As a result, the thermal cycle specimens had mixed fracture characteristics.

本文综合了当前可靠性分析及评价方法,分别从可靠性目标、流程、准备工作、建模及分析评价等方面,凝练总结了可靠性分析方法实施过程中的一些共性要求,规范了相关流程,为工程中实施和推广可靠性提拱了参考和指导.

随着动车组不断出新,人们对车内环保的要求愈发增多.本文从动车组零部件运输存放、生产过程中加热通风、除味剂施工等工艺方面对动车组车内环保管控措施进行介绍,并对未来车内环保管控的发展做出展望.

基于电化学原理和无线通信技术,研制了高速列车材料腐蚀状态智能监控系统,分别在海南文昌、湖北武汉、山东青岛三地的环境腐蚀试验站及京广高铁在役高速动车组上进行了部署,并连续开展了6个月以上的腐蚀数据在线采集及分析,掌握了动车组车体铝合金材料及涂层6个月的腐蚀老化规律,为预测车辆结构材料 的腐蚀风险、评估涂层的寿命衰减,加强动车组全生命周期安全管理提供了重要的数据支撑.

石墨电极接头作为一种新型高性能低成本冶炼金属的石墨材料,具有广泛的应用前景.然而,石墨电极接头在生产加工中却存在着很多问题,难以厘清.为了探明石墨电极接头锥面的加工性能,进行石墨电极接头锥面正交车削实验.实验选取不同刀具角度的硬质合金刀具进行不同车削参数实验,并进行分析.结果表明:加工石墨电极接头锥面时,切削力呈现波动状态,并且切削力大小随走刀速度f和切削厚度ap的增大而增大,随切削速度vc、刀具前角γ和后角α增大而减小.此外,由于石墨电极接头是脆性材料,γ增大时刀具并不会产生积削瘤.基于最小切削力和表面粗糙度目标,得到的最佳切削参数及刀具角度为ap=0.5 mm、vc=160 mm·min-1、f=100 mm·min-1、γ=12°、α=16°.得出的最优工艺参数及相关结论可为企业在生产实践中提供理论参考.