Study on Microstructures of tungsten-based high-density alloy laser welding-brazing jointWang, Haidong; Li, Baishun; Wang, Min; Ye, Ruan
doi: 10.1088/1742-6596/2954/1/012012pmid: N/A
The microstructure of tungsten-based high-density alloy laser fusion brazed joints was characterized by using optical microscopy, scanning electron microscopy, and X-ray diffractometer in this work. The results indicate that the laser fusion brazing joint includes a fusion welding joint and brazing joint; The weld seam consists of gray α-Ag, black β-Cu, and detached particles of tungsten alloy; β-Cu is distributed in the α-Ag substrate with blocky, rod, and strip morphology, and the layered α-Ag and β-Cu can be seen in some areas. The results reveal that the dominant intermetallic compound in the fusion zone is W particles, γ- (Fe, Ni), and FeNi3 intermetallic compounds. The dominant intermetallic compounds in the brazing seam are α-Ag and β-Cu. There is a compound-type interface in the laser fusion brazing joint of tungsten-based high-density alloy, and the intermetallic phase in the interface is FeZn7.
Synthesis of Ga-doped InP quantum dots with high fluorescence efficiency and its optical propertiesYang, Suolong; Zhao, Xiaochong; Yu, Huilong
doi: 10.1088/1742-6596/2954/1/012076pmid: N/A
Defects on the surface of InP quantum dots (QDs) often result in low photoluminescence quantum yields (PLQY). Herein, in order to improve the PLQY of InP QDs, Ga-doping was used to reduce the surface defect states of InP QDs and improve the PLQY. Firstly, Ga-doped InP QDs (Ga:InP QDs) were synthesized by the growth doping method, and the size uniformity, absorption spectra, and fluorescence spectra were characterized. Secondly, the effects of growth temperature and Ga doping concentration on the optical properties of QDs were studied. The experimental results show that the synthesized Ga:InP QDs are uniform in size, and their PLQY is significantly improved. The fluorescence color of Ga:InP QDs can be tuned by adjusting the In/P ratio and growth temperature. Synthesized Ga:InP QDs exhibited greatly increased PLQY up to 14%. In contrast, without Ga-doping, the PLQY of InP QDs only attained 0.4%. After subsequent coating with a ZnS shell, the resulting Ga:InP/ZnS core/shell structure QDs reached a high PLQY of 70% with a fluorescence emission at 640 nm.
In-situ X-ray computed tomography study on defect evolution in additively manufactured GH4169 superalloy during high-temperature fatigueWang, Hui; Pan, Jinchao; Huo, Shihui; Ma, Penghui; Wang, Ying
doi: 10.1088/1742-6596/2954/1/012122pmid: N/A
This study investigates the defect evolution mechanisms in nickel-based GH4169 superalloy fabricated using selective laser melting (SLM) under high-temperature fatigue. X-ray computed tomography (CT) was employed for three-dimensional defect characterization, and in-situ fatigue tests were conducted at 400°C. Initial defects were found to be randomly distributed, primarily consisting of pores and lack-of-fusion (LOF) defects, with 80% having an equivalent diameter smaller than 20 μm. Pores exhibited significant axial elongation during fatigue loading in stress-concentration regions, especially at elevated temperatures, where localized plastic deformation was enhanced. Additionally, fatigue cycling led to defect coalescence, with smaller defects merging into larger ones, primarily along the tensile loading direction.
Effect of aging regime on the microstructure, mechanical properties, and impact toughness of Al-Zn-Mg alloysZhou, Bin; Yu, Mingyang; Li, Xiwu; Yan, Hongwei
doi: 10.1088/1742-6596/2954/1/012088pmid: N/A
This article investigates the effects of different aging regimes on the microstructure, mechanical properties, and impact toughness of Al-Zn-Mg alloys. The mechanisms by which microstructural changes influence mechanical properties and impact toughness are discussed. In an overaged condition, as aging temperature is elevated and aging time extends, intragranular precipitates become coarser, and the density of precipitates decreases, leading to a decline in yield and tensile strength properties. However, it narrows the strength gap between intragranular and intergranular regions, enhancing the impact toughness. The appearance of the equilibrium η phase and the expansion of PFZ are also reasons for the improved impact toughness of the alloy.
Simulation study of solid-state phase transformation in IN738 superalloy by electron beam meltingKong, Haohao; Hou, Yaqing; Qin, Hailong; Sun, Zhimin; Xie, Jinli; Bi, Zhongnan; Su, Hang
doi: 10.1088/1742-6596/2954/1/012011pmid: N/A
A deep understanding of solid-state phase transformation behavior (SPTB) during the Electron Beam Melting (EBM) process is essential for achieving customized microstructures and properties. This study developed an SPTB prediction model by coupling an equivalent micro-zone heat source (EMHS) model with a non-isothermal Johnson-Mehl-Avrami (NJMA) kinetics model. We investigated the evolution of SPTB in IN738 alloy during a ten-layer, five-track continuous line melting process. The results indicate that the evolution of the γ′ phase can be categorized into three stages: precipitation complete dissolution stage, precipitation partial dissolution stage, and cooling stable precipitation stage. Due to temperature history differences during printing, the γ′ phase exhibits uneven distribution in the powder bed, with maximum volume fractions of 1.015e−7, 15.86, and 10.06 at the end of printing for the first, fifth, and tenth layers. Following cooling, these values increased to 3.098, 17.85, and 45.65. The model’s validity was verified using literature data. This research enhances understanding of EBM’s relationships between materials, processes, microstructures, and properties.
Study on the influence of forming process of I-shaped long stringer of civil aircraft composite materials on crippling performanceChang, Mingde; Ding, Hongbiao; Wu, Jiang
doi: 10.1088/1742-6596/2954/1/012025pmid: N/A
Crippling performance is an essential indicator of I-shaped long stringers used in civil aircraft composite wall panels. In order to study the effect of the composite molding process on crippling performance, this paper studies the effect of co-curing and co-bonding molding methods on crippling performance for I-shaped long stringers with impact damage. Furthermore, under the premise of co-curing molding, the effect of soft film and hard film processes on crippling performance is studied. Test articles were manufactured and tested for verification. The results showed that the crippling performance of co-cured composites was 1.21 times that of co-bonding, and the crippling performance of soft mold composites was 1.08 times that of hard mold, which provides a basis for composite wall panel designers to choose composite molding processes.
Research on the effect of finishing cooling temperature on low-temperature fracture toughness of pipeline steelFan, Yanqiu; Ma, Changwen; Li, Shaopo; Ding, Wenhua
doi: 10.1088/1742-6596/2954/1/012112pmid: N/A
For pipelines served in a cold environment, low-temperature toughness was one vital element to ensure safety during serving, and drop-weight tear test(DWTT) is the common indicator to reflect the low-temperature toughness of pipeline steel. As we all know, there were many factors that influence low-temperature toughness, but studies were not sufficient regarding the effect of finishing cooling temperature. So, in this paper, the influence of finishing cooling temperature on low-temperature fracture toughness of pipeline steel was researched, and mechanical properties, microstructure, the fracture surface of DWTT samples, and grain boundary characteristics were observed and analyzed. After the same rolling treatment, three plates were cooled to 450°C, 500°C, and 550°C, respectively. The results showed that although three plates were cooled to different temperatures, the main type of microstructure remained the same, mainly quasi-polygonal ferrite and the small proportion of martensite-austenite islands, and average grain size gradually became smaller. When the finishing cooling temperature increased, the strength, including yield and tensile strength, climbed down, and sample 2 had the highest drop weight tear area of 92%, representing the highest low-temperature fracture toughness. The high-angle grain boundary densities of the three specimens were 0.413μm−1, 0.738μm−1 and 0.562μm−1, respectively. On the whole, specimen 2 had the best low-temperature toughness. It was mainly because the high-angle grain boundary density of specimen 2 was the largest, and high-angle grain boundary density can prominently prohibit crack propagation and boost low-temperature fracture ductility.
Effect of laser power on the microstructure and properties of laser cladding Ti-Al-Si composite coatingsChen, Haojie; Zhao, Haitao; Du, Chunyan; Zhao, Hui; Gong, Xun; Wang, Tao
doi: 10.1088/1742-6596/2954/1/012017pmid: N/A
Composite coatings with in-situ-grown ceramic phases were created using Ti-35Al-15Si as the cladding material and laser cladding coaxial powder feeding method. The effect of laser power on the quality, organization, and properties of coatings was examined. The experimental results reveal that as laser power rises, penetrating cracks form in the cladding layer. Its fused cladding layer consists mainly of Ti-Al and Ti-Si phases. When the laser power increases, the dilution rate of the cladding layer also rises, resulting in an increase in the Ti-Al phase and a decrease in the Ti-Si phase. Its fused cladding layer’s hardness and wear resistance declined as laser power increased, peaking at 900 W and 829.36 HV.
Four-wheel, eight-wheel drive mobile robot designLin, Sheng; Chen, Shushuai; Jiang, Tao; Zhang, Dongliang; Sun, Youjia
doi: 10.1088/1742-6596/2954/1/012057pmid: N/A
The purpose of this paper is to design and analyze a mechanical system of a four-wheeled eight-wheel drive mobile robot to cope with complex terrain and high-load environments. The walking and steering systems are designed to be independently driven by brushless DC motors for each wheel. The chassis structure is optimized. High-efficiency mechanical transmission devices are used to achieve precise power transmission and control. The designed four-wheeled eight-wheel drive mobile robot can flexibly adjust the steering, smoothly pass through different obstacles, and maintain a good operating condition under high load conditions. It significantly improves mobility and stability in complex terrain, effectively improves power transmission efficiency and system reliability, is suitable for various complex application scenarios, and has a wide range of application prospects.
Numerical simulation research of mechanical properties for pipelayer ROPS with welded seamsZhao, Keli; Niu, Zhongyue; Hao, Zhentao; Zhang, Xueyun
doi: 10.1088/1742-6596/2954/1/012085pmid: N/A
This paper presents a simulation analysis of the Roll-Over Protection Structure (ROPS) for a crawler pipelayer’s cab, focusing on the impact of weld seams on performance. Comparative simulations with and without weld seams were conducted using Ansys Workbench. The results indicate that the weld presence can enhance lateral energy absorption by up to 731.21 J, with an average increase of 4.405%. The study also utilized the XGBoost algorithm to predict weld fractures and applied birth-death element technology to manage them effectively. The findings provide new insights into the design of ROPS for crawler pipelayers, highlighting the importance of considering weld impacts in simulation analysis and providing a theoretical basis for further structural optimization.