9 results on '"Xinqi Yang"'
Search Results
2. Texture features and strengthening mechanisms in welding nugget zone of SSFSWed thick-plate Al–Li alloy joint
- Author
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Chao Gu, Xinqi Yang, Wenshen Tang, Yongsheng Xu, and Chaobo Tian
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
3. The influence of post-weld tempering temperatures on microstructure and strength in the stir zone of friction stir welded reduced activation ferritic/martensitic steel
- Author
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Napat Vajragupta, Huijun Li, Wenshen Tang, Shengli Li, Xinqi Yang, and Alexander Hartmaier
- Subjects
010302 applied physics ,Materials science ,Mechanical Engineering ,Metallurgy ,02 engineering and technology ,Welding ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,law.invention ,Mechanics of Materials ,law ,Martensite ,0103 physical sciences ,Ultimate tensile strength ,Friction stir welding ,General Materials Science ,Tempering ,Dislocation ,0210 nano-technology ,Electron backscatter diffraction - Abstract
Reduced activation ferritic/martensitic (RAFM) steels are among the most competitive candidates of structural materials for nuclear fusion reactors, due to their superior comprehensive properties. Friction stir welding (FSW) was investigated in joining RAFM steel, considering its potential advantages in obtaining an optimal microstructure and mechanical properties of welded joint. To evaluate the feasibility of FSW in joining RAFM steel, an in-depth understanding of the microstructure-property relationships for friction stir welded joints of RAFM steel is necessary. In this research, the quantitative relationships between microstructural evolution and tensile properties in the stir zone (SZ) of friction stir welded RAFM steel after post-weld tempering treatment (PWTT) were systematically studied. Three different post-weld tempering temperatures namely 720 °C, 760 °C, and 800 °C were adopted. Then the uniaxial tensile properties were tested at room temperature and 550 °C, respectively. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and the Thermo-Calc Calphad software were adopted to systematically investigate the microstructural evolution. Martensite lath width, precipitate number density, equilibrium solid solubility of alloying elements in the matrix, and geometrically necessary dislocation (GND) density were analyzed quantitatively. With the results obtained, we assessed the contribution of each strengthening mechanism to the 0.2% offset yield strength. According to the effective inter-barrier spacing theory, a microstructure-sensitive yield strength model was obtained to well predict the change in yield strength at different conditions. Finally, the results calculated by equivalent strengthening effect indicated that the crucial microstructure determining the yield strength of the SZ for RAFM steel after PWTT is the high density of dislocation substructures.
- Published
- 2021
4. Microstructural characteristics and mechanical heterogeneity of underwater wet friction taper plug welded joints for low-alloy pipeline steel
- Author
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Kaixuan Liu, Xinqi Yang, Wei Lin, and Junzhen Xiong
- Subjects
Equiaxed crystals ,Materials science ,Bainite ,Mechanical Engineering ,Metallurgy ,02 engineering and technology ,Welding ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,020501 mining & metallurgy ,law.invention ,0205 materials engineering ,Mechanics of Materials ,law ,Martensite ,Ferrite (magnet) ,General Materials Science ,Friction welding ,Composite material ,0210 nano-technology ,Joint (geology) - Abstract
Underwater wet friction taper plug welding experiments have been performed on X52 pipeline steel with 6500–7500 rpm rotational speeds at 30–45 kN axial forces, and the microstructural characteristics and mechanical heterogeneity of defect-free friction taper plug welded joints are discussed thoroughly. It is found that the microstructure of welded joint is remarkably inhomogeneous and very different from the base metal. The welded joint has dramatically coarse grains and is dominantly characterized by a mixture of quenched martensite, upper bainite and various types of ferrites including Widmanstatten ferrite. Unlike the traditional solid-state friction welding processes, the relative homogeneous microstructure with fine and equiaxed grains cannot be obtained in the friction taper plug welding process. The axial force has a greater impact on microstructure of welded joint as compared to rotational speed. The hardness profiles measured in cross-section of welded joints are severely non-uniform, ranging from 200 to 400 HV1, due to the inhomogeneity of microstructure. The impact absorbed energy of welded joint with V-notch in the bonding zone was considerably lower than that of base material (about only 20% of parent metal) because of the local obviously coarse grain, Widmanstatten ferrite and banding ferrite defect. The microstructural inhomogeneity results in mechanical heterogeneity.
- Published
- 2017
5. Weakening mechanism and tensile fracture behavior of AA 2219-T87 friction plug welds
- Author
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Dongpo Wang, Bo Du, Xinqi Yang, Lei Cui, and Zhuanping Sun
- Subjects
0209 industrial biotechnology ,Heat-affected zone ,Materials science ,Mechanical Engineering ,Metallurgy ,02 engineering and technology ,Welding ,Condensed Matter Physics ,law.invention ,020303 mechanical engineering & transports ,020901 industrial engineering & automation ,0203 mechanical engineering ,Mechanics of Materials ,law ,Dimple ,Ultimate tensile strength ,Fracture (geology) ,Dynamic recrystallization ,General Materials Science ,Spark plug ,Joint (geology) - Abstract
In this paper, the weakening mechanism and tensile fracture behavior of AA 2219-T87 friction plug weld were investigated. The as welded friction plug joint involves six regions of plug metal (PM), plug thermo-mechanically affected zone (PTMAZ), recrystallized zone (RZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ), and base metal (BM). Owing to the severe material flow and plastic deformation at high welding temperatures, dynamic recrystallization would occur near the bonding interface. In TMAZ and HAZ, dissolution of θ′ phase, θ′ to θ transformation and coarsening of θ particles are observed. Throughout the weld, the minimum hardness value 87Hv is found in TMAZ near RZ. During tensile process, the initial strain concentration generates in TMAZ, and then intensifies and extends until eventual fracture of the joint. The fracture morphology of the joint is characterized by large and shallow dimples with second phases.
- Published
- 2017
6. Characteristics of friction plug welding to 10 mm thick AA2219-T87 sheet: Weld formation, microstructure and mechanical property
- Author
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Xinqi Yang, Jianling Song, Bo Du, Zhongping Zhang, Zhuanping Sun, and Lei Cui
- Subjects
0209 industrial biotechnology ,Heat-affected zone ,Materials science ,Mechanical Engineering ,Alloy ,Metallurgy ,02 engineering and technology ,Welding ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Material flow ,law.invention ,020901 industrial engineering & automation ,Mechanics of Materials ,Dimple ,law ,Ultimate tensile strength ,engineering ,General Materials Science ,0210 nano-technology ,Spark plug - Abstract
In this paper, friction plug welding (FPW) experiments of 2219-T87 aluminum alloy sheets with 10 mm thickness were performed. The material flow behavior, microstructures, second phases, mechanical properties and failure behaviors were also investigated. The results indicate that a sufficient volume of material from both plug and base metal flow upward and downward is critical obtaining defect free weld. The plug thermo-mechanically affected zone, plug recrystallized zone, thermo-mechanically affected zone (TMAZ), and heat affected zone could be weakened significantly owing to the thermal–mechanical process. The main reason is believed as the dissolution of precipitates and the redistribution of constituent particles. The maximum tensile strength and elongation of the joint would reach 329 MPa and 7%, respectively. The TMAZ closest to the bonding interface is the weakest location of the joints. The tensile crack initiates at TMAZ close to the bonding interface near the lower surface and then propagates along the soften area in TMAZ with forming a large amount of dimples with second phases existing at the bottom.
- Published
- 2016
7. Characteristics of defects and tensile behaviors on friction stir welded AA6061-T4 T-joints
- Author
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Guang Zhou, Zhikang Shen, Xiaodong Xu, Xinqi Yang, and Lei Cui
- Subjects
musculoskeletal diseases ,Materials science ,Mechanical Engineering ,Metallurgy ,technology, industry, and agriculture ,Welding ,Zigzag line ,Condensed Matter Physics ,law.invention ,Mechanics of Materials ,law ,Joint line ,Ultimate tensile strength ,Fracture (geology) ,Friction stir welding ,General Materials Science ,Composite material ,Severe plastic deformation - Abstract
In the present study, AA6061-T4 T-joints were successfully fabricated by friction stir welding (FSW) in three different combination ways of skins and stringers. Distributions and formation mechanisms of tunnel defects, kissing bond defects, original joint line with severe plastic deformation (OJLwSPD) defects, and zigzag line defects in T-joints were investigated by macro- and micro-observations. Influences of defects distributions and welding parameters on the tensile behaviors of T-joints were examined. To a better understanding of failure behaviors of T-joints, fracture locations and fracture surfaces of tensile samples were also investigated.
- Published
- 2012
8. Comparative study on fatigue properties between AA2024-T4 friction stir welds and base materials
- Author
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Shusheng Di, Bo Jian, Guohong Luan, and Xinqi Yang
- Subjects
Materials science ,Mechanical Engineering ,Metallurgy ,Alloy ,Base (geometry) ,chemistry.chemical_element ,Eurocode ,Welding ,engineering.material ,Condensed Matter Physics ,Fatigue limit ,law.invention ,chemistry ,Mechanics of Materials ,law ,Aluminium ,visual_art ,Aluminium alloy ,visual_art.visual_art_medium ,engineering ,Friction stir welding ,General Materials Science - Abstract
The comparative study on fatigue properties between AA2024-T4 friction stir welds and base materials have been performed and the influence of zigzag-curve defects across weld section on the fatigue properties of FSW joints were investigated. It was shown that the zigzag-curve defects were the inherent feature existed in the friction stir nugget and could make the characteristic fatigue strength decrease from 96.19 MPa for base material to 73.71 MPa for welded joints with a reduction of 23.4%. Although the lower fatigue strength than the corresponding base material, the FSW joints of AA2024-T4 Al alloy achieved higher fatigue strength compared to the traditional fusion design curves IIW FAT40 and Draft Eurocode 9 design category 55-6 for structural aluminum alloy components.
- Published
- 2006
9. Effect of root flaws on the fatigue property of friction stir welds in 2024-T3 aluminum alloys
- Author
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Xinqi Yang, Caizhi Zhou, and Guohong Luan
- Subjects
Materials science ,Mechanical Engineering ,Metallurgy ,chemistry.chemical_element ,Welding ,Condensed Matter Physics ,Fatigue limit ,law.invention ,chemistry ,Mechanics of Materials ,Aluminium ,law ,visual_art ,Aluminium alloy ,visual_art.visual_art_medium ,Butt joint ,Friction stir welding ,General Materials Science - Abstract
The fatigue experiment of friction stir (FS) welds in 2024-T3 aluminum alloys were performed to investigate the influence of root flaws on the fatigue strength and life of FS welds. The test results of welds with flaws (flawed welds) were compared with the results suggested by the International Institute of Welding (IIW) recommendations and the welds without root flaws (flaw-free) in the published research reports. It was found that there was always existed flaws at the roots of FS welds because of unsuitable welding parameters and the vertical length of the flaws is about 0.31–0.33 mm for the FS butt-welded joint of 4 mm in thickness. The fatigue life of flawed welds is 33–80 times shorter than that of flaw-free welds, and the fatigue characteristic values have decreased from 120.6 MPa for flaw-free welds to 54.7 MPa for flawed welds at 2 × 106 cycles.
- Published
- 2006
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