33 results on '"Xinqi Yang"'
Search Results
2. Microstructure heterogeneity and mechanical properties of Mg-Gd-Y-Zr alloy fabricated by force-controlled additive friction stir deposition
- Author
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Ting Luo, Wenshen Tang, Ruilin Wang, Shiwei Wang, Lv Xiao, and Xinqi Yang
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2023
3. Interfacial grain structure, texture and tensile behavior of multilayer deformation-based additively manufactured Al 6061 alloy
- Author
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Wenshen Tang, Xinqi Yang, Chaobo Tian, and Yongsheng Xu
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2023
4. Effect of rotation speed on microstructure and mechanical anisotropy of Al-5083 alloy builds fabricated by friction extrusion additive manufacturing
- Author
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Wenshen Tang, Xinqi Yang, Chaobo Tian, and Chao Gu
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
5. Effect of microstructure heterogeneity on the mechanical properties of friction stir welded reduced activation ferritic/martensitic steel
- Author
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Wenshen Tang, Xinqi Yang, Napat Vajragupta, Shengli Li, Aleksander Kostka, Hao Wang, Abhishek Biswas, and Alexander Hartmaier
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Materials science ,Friction stir welding ,Mechanical Engineering ,Metals and Alloys ,Welding ,Condensed Matter Physics ,Microstructure ,Reduced activation ferritic/martensitic steel ,Indentation hardness ,Martensitic microstructure ,law.invention ,Electron backscatter diffraction orientation analysis ,Mechanics of Materials ,law ,Martensite ,Geometrically necessary dislocations ,General Materials Science ,Austenite reconstruction ,Dislocation ,Composite material ,Electron backscatter diffraction - Abstract
The microhardness distribution in the different zones of a friction stir welded reduced activation ferritic/martensitic steel has been investigated and correlated to the hierarchical martensitic microstructure in the respective zones, characterized by electron backscatter diffraction orientation analysis. It is found that the variation of prior austenite grain size, packet size, and block width in different subzones is influenced by the peak temperature and effective strain rate during the friction stir welding process. The distribution of the microhardness correlates directly with the geometrically necessary dislocation density observed in the different zones.
- Published
- 2022
6. Characteristics of Friction Plug Joints for AA2219-T87 FSW Welds
- Author
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Zhuanping Sun, Xinqi Yang, and Shuxin Li
- Subjects
AA2219-T87 aluminum alloy ,fiction plug welding ,plug and plate hole ,mechanical property ,microstructure ,local strength ,General Materials Science - Abstract
In this study, Friction plug welding (FPW) for 8 mm thickness AA2219-T87 sheets were carried out, and defect-free joints were obtained. The geometric size of plug and plate hole, rotational speed and welding force exhibit significant effects on the weld formation. Meanwhile, it is concluded that significant inhomogeneity of microstructure and mechanical properties exists in FPW joints. The recrystallization zone has the highest mechanical properties owing to the fine equiaxed grains and uniformly distributed θ precipitates. The entire plug, thermo-mechanically affected zone and nugget thermo-mechanically affected zone closed to the bonding interface are significantly softened due to the deformation of the grains and θ’ precipitate dissolution. The ultimate tensile strength (UTS) and elongation of the FPW joints can reach 359 MPa and 7.3% at 77 K and 305 MPa and 5% at 298 K, respectively.
- Published
- 2021
7. Effect of cube texture on local softening of stationary shoulder friction stir welding for thick-plate Al-Li alloy
- Author
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Chao Gu, Xinqi Yang, Wenshen Tang, Chaobo Tian, and Yongsheng Xu
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
8. 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
9. Revisiting the preparation of titanium dioxide: aerosol-assisted production of photocatalyst with higher catalytic activity than P25
- Author
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Jingjing Zhan, Xiujuan Zhang, Xinqi Yang, Yang Liu, Zhichen Si, Hongkun Chen, Chen Xiaofei, and Hao Zhou
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Materials science ,020502 materials ,Mechanical Engineering ,02 engineering and technology ,Catalysis ,chemistry.chemical_compound ,symbols.namesake ,Reaction rate constant ,0205 materials engineering ,chemistry ,X-ray photoelectron spectroscopy ,Chemical engineering ,Mechanics of Materials ,Titanium dioxide ,Methyl orange ,symbols ,Photocatalysis ,Particle ,General Materials Science ,Raman spectroscopy - Abstract
This research revisited the preparation of the pure titanium dioxide. Through the aerosol-assisted technology and our self-made setup, a kind of titanium dioxide with higher activity than commercial product P25 was successfully fabricated, while this aerosol-assisted process takes only about 10 s. By adjusting the operation temperature, the obtained titanium dioxide nanoparticles have different crystalline sizes and phase compositions, which are two major factors determining the catalytic activity of the materials. The results show that the optimum temperature was 600 °C, and the AST-600 particle prepared under this condition has the rate constant at 1.49 in the removal of methyl orange, which is 2.36 times that of Degussa P25. Although the AST-600 particle could only be activated by UV light similar to P25, the efficiency of AST-600/g-C3N4 is higher than that of P25/g-C3N4 under the visible condition. Meanwhile, the as-prepared titanium dioxide particles have been thoroughly characterized by TEM, SEM, XRD, PL, XPS, DRS, Raman and nitrogen adsorption in the study. Hence, we prepared a pure titanium dioxide with higher catalytic activity than P25, but the process is still very convenient, low cost and easy to scale up, holding great potential as an alternative to commercial product P25.
- Published
- 2019
10. Microstructural characteristics and mechanical properties of friction-stir-welded modified 9Cr–1Mo steel
- Author
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Shengli Li, Huijun Li, Wenshen Tang, Xinqi Yang, and Feixiang Wang
- Subjects
Heat-affected zone ,Materials science ,Scanning electron microscope ,020502 materials ,Mechanical Engineering ,02 engineering and technology ,Welding ,Microstructure ,law.invention ,0205 materials engineering ,Mechanics of Materials ,law ,Martensite ,Ultimate tensile strength ,Friction stir welding ,General Materials Science ,Composite material ,Electron backscatter diffraction - Abstract
The modified 9Cr–1Mo steel was selected to conduct friction stir welding experiment. Defect-free welded joints were successfully obtained with the welding parameters of 300 rpm–50 mm/min and 400 rpm–50 mm/min. The microstructures of the welded joint were observed by scanning electron microscopy, electron backscatter diffraction and transmission electron microscope. The main microstructural characteristics of the weld zone (WZ) and the high-temperature heat affected zone are the formation of fresh quenched martensite, dissolution of M23C6 carbides, grain refinement and increase in kernel average misorientation. The WZ is significantly hardened, and the maximum hardness of this region is about twice that of the base material (BM). The ultimate tensile strength of the welded joint is up to 98% that of BM. The absorbed impact energies of the SZ and HAZ reach 77.8% and 87.4% that of the BM, respectively. Besides, the influence of post weld heat treatment on the microstructure and mechanical properties of the welded joint was also investigated.
- Published
- 2019
11. 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
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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
12. Zigzag line defect in friction stir butt-weld of ferritic stainless steel
- Author
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Huijun Li, Shengli Li, Wenshen Tang, and Xinqi Yang
- Subjects
Materials science ,Impact toughness ,Mechanical Engineering ,Butt welding ,Fracture mechanics ,02 engineering and technology ,Zigzag line ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Mechanics of Materials ,Ultimate tensile strength ,General Materials Science ,Composite material ,0210 nano-technology ,Joint (geology) - Abstract
A zigzag line defect was detected in the stir zone (SZ) of friction stir butt-welded 12% Cr ferritic stainless steel joint. The characteristics and formation cause of the zigzag line defect was clarified and analyzed. The zigzag line defect presented the partly bonded feature but with relatively higher hardness, which did not affect the tensile properties at room temperature of the joint. The micro-void features of the zigzag line defect were considered to promote crack propagation under impact load, thereby significantly reducing the impact toughness of the SZ.
- Published
- 2021
13. 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
14. 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
15. Synthesis of star-branched PLA-b-PMPC copolymer micelles as long blood circulation vectors to enhance tumor-targeted delivery of hydrophobic drugs in vivo
- Author
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Xubo Yuan, Ke Li, Jin Zhao, Li-mei Wang, Lixia Long, Jinjin Sun, Xiao-ming Qian, Xinqi Yang, Yu Ren, Li-gang He, Chunsheng Kang, and Chaoyong Liu
- Subjects
Materials science ,Atom-transfer radical-polymerization ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Micelle ,Ring-opening polymerization ,0104 chemical sciences ,chemistry.chemical_compound ,Polylactic acid ,chemistry ,Polymer chemistry ,Drug delivery ,Biophysics ,Click chemistry ,Copolymer ,General Materials Science ,Nanocarriers ,0210 nano-technology - Abstract
Star-branched amphiphilic copolymer nanocarriers with high-density zwitterionic shell show great promise in drug delivery due to their controllable small size and excellent anti-biofouling properties. This gives the hydrophobic cargo with high stability and long blood circulation in vivo . In the present study, star-branched polylactic acid and poly(2-methacryloyloxyethyl phosphorylcholine) copolymers with (AB 3 ) 3 –type architecture (PLA- b -PMPC 3 ) 3 were conceived as drug vectors, and the copolymers were synthesized by an “arm-first” approach via the combination of ring opening polymerization (ROP), atom transfer radical polymerization (ATRP) and the click reaction. The self-assembled star-branched copolymer micelles (sCPM) had an average diameter of about 64.5 nm and exhibited an ultra-hydrophilic surface with an ultralow water contact angle of about 12.7°, which efficiently suppressed the adhesion of serum proteins. In vivo experiments showed that the sCPM loading strongly enhanced the blood circulation time of DiI and the plasma half-life of DiI in sCPM was 19.3 h. The relative accumulation concentration in tumor of DiI delivered by sCPM was 2.37-fold higher than that of PLA-PEG, at 4 h after intravenous injection. These results demonstrated that the star-branched copolymer (PLA- b -PMPC 3 ) 3 is a promising alternative carrier material for intravenous delivery versus classic PEG-modified strategies.
- Published
- 2016
16. Fabricating Defect-Free API X65 Steel Welds under Underwater Wet Conditions using Friction Taper Plug Welding
- Author
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Feixiang Wang, Lei Cui, Xinqi Yang, and Yayun Yin
- Subjects
010302 applied physics ,Heat-affected zone ,Materials science ,Bainite ,Mechanical Engineering ,Metallurgy ,02 engineering and technology ,Welding ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Industrial and Manufacturing Engineering ,Acicular ferrite ,law.invention ,Mechanics of Materials ,law ,Ferrite (iron) ,Martensite ,0103 physical sciences ,engineering ,General Materials Science ,Composite material ,0210 nano-technology - Abstract
The experiment on API X65 steel was carried out using friction taper plug welding (FTPW) under underwater wet conditions at room temperature. Sound weld formation can be achieved vastly at axial force ranging from 25 to 40 kN and a rotating speed of 7000 rpm. The microstructure of the weld zone consists of lath martensite, upper bainite, granular bainite, polygonal ferrite, and acicular ferrite. The microstructure of heat affected zone (HAZ) mainly consists of lath bainite as well as a bit of lath martensite and granular bainite. The tensile properties of defect-free welds are excellent. The maximum impact energy of the V-notch of bonding area can reach 110 J, which was conducted at 0°C with an error of ±12.5 J. The typical SEM impact fracture morphology presents areas of cleavage, quasi-cleavage, and dimples.
- Published
- 2016
17. Microstructure and mechanical properties of underwater friction taper plug weld on X65 steel with carbon and stainless steel plugs
- Author
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W. Xu, J. Cao, Yayun Yin, Xinqi Yang, and Lei Cui
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Austenite ,0209 industrial biotechnology ,Materials science ,Bainite ,Metallurgy ,02 engineering and technology ,Welding ,Lath ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,law.invention ,020901 industrial engineering & automation ,law ,Residual stress ,Martensite ,engineering ,General Materials Science ,Composite material ,0210 nano-technology ,Spark plug - Abstract
Underwater friction taper plug welding for X65 pipeline steel was performed using Q345 structural steel and 316L stainless steel plugs. Weld microstructures, defects formation and mechanical properties were investigated. Using Q345 plugs can produce defect free and overmatching welded joints whose impact toughness was also favourable. Lower bainite and lath martensite in the weld zone resulted in high hardness with maximum value up to 418 HV10. Using 316L plugs can significantly reduce weld zone hardness due to austenite dominated microstructure. Microcracks can easily emerge at and may propagate along γ–δ phase boundaries to form macrocracks. Intermittent cracks were found along the bonding interface of all the 316L plug welds, which should be caused by the relief of the residual stress.
- Published
- 2016
18. 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
19. The local strength and toughness for stationary shoulder friction stir weld on AA6061-T6 alloy
- Author
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Xinqi Yang, Zhuanping Sun, Dongxiao Li, and Lei Cui
- Subjects
0209 industrial biotechnology ,Toughness ,Materials science ,Mechanical Engineering ,Metallurgy ,Alloy ,02 engineering and technology ,Welding ,engineering.material ,Plasticity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,law.invention ,020901 industrial engineering & automation ,Mechanics of Materials ,law ,Ultimate tensile strength ,engineering ,Particle ,General Materials Science ,Composite material ,0210 nano-technology ,Base metal - Abstract
In this study, the local microstructure, strength and toughness of different zones in AA6061-T6 stationary shoulder friction stir welds were investigated. Results indicated that, the most significant weakening for both strength and toughness is found in HAZ that close to NZ. The microstructure of NZ includes recrystallized fine grains with high density of dislocations, homogeneous constituent particles distribution and re-precipitated of G.P. zones resulting in the recovery of local strength and the improvement for both plasticity and toughness. In HAZ, the grain structure and constituent particle distribution inherit the characteristics of base metal, but β″ precipitates are dissolved and the reprecipitated β′ particles are coarsened. This results in the decrease of yield strength, tensile strength, crack initial energy and propagation energy of HAZ, especially near NZ.
- Published
- 2016
20. Material flow influence on the weld formation and mechanical performance in underwater friction taper plug welds for pipeline steel
- Author
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Xinqi Yang, Lei Cui, Yayun Yin, Shengli Li, and Feixiang Wang
- Subjects
Heat-affected zone ,Weld access hole ,Materials science ,Mechanical Engineering ,Metallurgy ,Welding ,Microstructure ,Electric resistance welding ,Material flow ,law.invention ,Mechanics of Materials ,law ,Ultimate tensile strength ,lcsh:TA401-492 ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Friction welding ,Composite material - Abstract
Friction taper plug welding experiment was conducted on X65 pipeline steel in underwater wet condition. Results indicate that the weld defects, microstructural evolution and mechanical properties are closely related to the material flow behavior during welding. The formation of weld defect characterized by incomplete filling or lack of bonding is mainly caused by the poor flowing property of the plug material especially in low axial welding force. In the experiment condition, rising the axial force would result in better material flow, higher weld power, more energy input and further improve the bond quality of the weld. Microstructure of both weld zone and heat-affected-zone mainly consists of lath bainite which results in an overmatching condition through the weld. High quality welds in this study also exhibit good tensile and impact properties that is equal to the base metal and acceptable bend property of 105° as the best. Keywords: Underwater welding, Friction taper plug welding, Material flow, Mechanical properties, Pipeline steel
- Published
- 2015
21. Fatigue property of stationary shoulder friction stir welded additive and non-additive T joints
- Author
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Xinqi Yang, Xiang Zhang, Dongxiao Li, Fangzhou He, and Lei Cui
- Subjects
musculoskeletal diseases ,Materials science ,Metallurgy ,technology, industry, and agriculture ,Fatigue testing ,Welding ,Condensed Matter Physics ,Microstructure ,law.invention ,law ,Fracture (geology) ,Bending fatigue test ,Friction stir welding ,General Materials Science ,Composite material ,Joint (geology) ,Stress concentration - Abstract
Additive and non-additive T joints were successfully fabricated by stationary shoulder friction stir welding using various welding parameters. No interior defects were observed in all joints by microstructural examination. The fatigue property of both additive and non-additive joints was revealed by four-point bending fatigue test. The microstructure and the stress concentration were investigated at the fatigue crack initiation sites of various T joints. Stress concentration determines the fracture location, and the surface microstructure influences the fatigue property. The stress concentration at the internal corner was evidently lower for additive joint than non-additive joint. The surface of stationary shoulder friction welded joint was characterised by ultrafine grains, which evidently enhanced the fatigue property.
- Published
- 2015
22. Influence of processing parameters on microstructure and mechanical performance of refill friction stir spot welded 7075-T6 aluminium alloy
- Author
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J. S. C. Hou, Xinqi Yang, Y. Chen, Adrian P. Gerlich, and Zhikang Shen
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Heat-affected zone ,Materials science ,Scanning electron microscope ,Metallurgy ,Welding ,Condensed Matter Physics ,Microstructure ,law.invention ,Optical microscope ,law ,visual_art ,Aluminium alloy ,visual_art.visual_art_medium ,Shear strength ,General Materials Science ,Spot welding - Abstract
Refill friction stir spot welding (FSSW) is a solid state joining technology recently derived from conventional FSSW. In the present study, refill FSSW was performed in a 0·8 mm thick AA7075-T6 aluminium alloy with varying welding parameters (welding time and plunge depth). The influence of welding parameters on the microstructure and mechanical properties of the weld was investigated in terms of nugget thickness, hardness and overlap shear strength. The microstructural features and fracture mechanism were observed by optical microscopy and scanning electron microscopy. The results indicate that the nugget thickness increases with increasing welding time and plunge depth. Furthermore, melted films observed in the stir zone (SZ) were consistent with a maximum temperature of 470·9°C measured 2·6 mm away from the SZ. The overlap shear strength increases with the increase of weld time and plunge depth due to increasing nugget diameter.
- Published
- 2014
23. Pipe Crack Recognition Based on Eddy Current NDT and 2D Impedance Characteristics
- Author
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Xinqi Yang, Wenbo Xuan, Hao Feng, Lianshuang Dai, Ting Wang, and Ziqian Liang
- Subjects
neural network ,Computer science ,image-processing ,Acoustics ,Pipeline (computing) ,02 engineering and technology ,lcsh:Technology ,01 natural sciences ,eddy current NDT ,Hough transform ,law.invention ,lcsh:Chemistry ,girth welds ,law ,Nondestructive testing ,Eddy-current testing ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Eddy current ,General Materials Science ,lcsh:QH301-705.5 ,Instrumentation ,Electrical impedance ,010302 applied physics ,Fluid Flow and Transfer Processes ,lcsh:T ,business.industry ,Process Chemistry and Technology ,020208 electrical & electronic engineering ,Ultrasonic testing ,General Engineering ,Magnetic flux leakage ,lcsh:QC1-999 ,Computer Science Applications ,lcsh:Biology (General) ,lcsh:QD1-999 ,lcsh:TA1-2040 ,lcsh:Engineering (General). Civil engineering (General) ,business ,lcsh:Physics - Abstract
Girth weld cracking of long-distance oil and gas pipelines yields substantial harm to pipeline safety and may cause serious accidents. As of today, non-destructive testing has been one of the most common methods for predicting potential faults and ensuring safe operation. Classical pipeline non-destructive testing methods include magnetic flux leakage testing and the use of ultrasonic testing by electromagnetic acoustic transducers. However, they are incapable of identifying the defects in complex surfaces like girth welds. Magnetic flux leakage testing exhibits poor anti-interference abilities and low space resolution. Ultrasonic testing by electromagnetic acoustic transducers suffer from low conversion efficiency and poor signal quality. In order to overcome the disadvantages of conventional pipeline non-destructive testing methods, we propose an embedded eddy current testing system by leveraging image processing and neural networks. Hough transform and the contour extraction technique are employed to extract the characteristic features from the two-dimensional (2D) eddy current impedance image. Experiment results show that the system can effectively identify the girth weld defects, featuring an accuracy of up to 92%. The low power consumption and compactness of the proposed system makes it a great candidate for pipeline inner inspection.
- Published
- 2019
24. 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
25. The influence of zigzag-curve defect on the fatigue properties of friction stir welds in 7075-T6 Al alloy
- Author
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Xinqi Yang, Guohong Luan, Shusheng Di, and Dapeng Fang
- Subjects
Materials science ,Metallurgy ,Alloy ,chemistry.chemical_element ,Eurocode ,Welding ,engineering.material ,Condensed Matter Physics ,Microstructure ,Fatigue limit ,law.invention ,Zigzag ,chemistry ,Aluminium ,law ,engineering ,Friction stir welding ,General Materials Science - Abstract
The microstructure and fatigue properties of friction stir welded joints of 7075-T6 Al alloy were discussed. It was shown that the zigzag-curve defect at the root of welds is the key factor to reduce the fatigue performance of single-sided friction stir welded joints of 7075-T6 high strength aluminum alloy. On the other hand, the FSW joints of 7075-T6 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
- 2007
26. 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
27. Investigation of microstructures and fatigue properties of friction stir welded Al–Mg alloy
- Author
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Caizhi Zhou, Xinqi Yang, and Guohong Luan
- Subjects
Materials science ,Alloy ,Metallurgy ,Fracture mechanics ,Welding ,engineering.material ,Condensed Matter Physics ,Microstructure ,Fatigue limit ,law.invention ,law ,Fracture (geology) ,engineering ,Friction stir welding ,General Materials Science ,Joint (geology) - Abstract
FS welds have a sound joint for the lack of voids, cracks and distortions. When compared to the base material, friction stir welding (FSW) joints exhibit a finer crystal grain in the weld nugget, and advancing side has a clearer boundary with the weld nugget than that of the retreating side. The fatigue life of FS welds is 6–14 times longer than that of MIG-pulse welds under the stress ratio R = 0.1 and the calculated fatigue characteristic values of each weld increase from 42.32 MPa for MIG to 68.47 MPa for FSW at 2 × 10 6 cycles. In the high-cycle regime, the fatigue strength of the FSW joint is almost equivalent to that of the base material. The fatigue fracture of FSW revealed regions of crack initiation, stable crack growth and overload.
- Published
- 2006
28. Effect of oxide array on the fatigue property of friction stir welds
- Author
-
Caizhi Zhou, Guohong Luan, and Xinqi Yang
- Subjects
Materials science ,Stress ratio ,Mechanical Engineering ,Butt welding ,Metallurgy ,Metals and Alloys ,Oxide ,Condensed Matter Physics ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Fatigue loading ,Friction stir welding ,General Materials Science ,Friction welding - Abstract
The fatigue behaviour of single-sided friction stir (FS) butt welds containing oxide array was investigated. The oxide array makes cracks initiate easily under fatigue loading, and has a deleterious effect on the fatigue properties of FS welds. The fatigue characteristic values of FS welds with oxide array have been decreased by 35% for 5083 welds and 55% for 2024 welds at 2 × 10 6 cycles. The fatigue lives of FS welds with oxide array were 20–40 times shorter for Al 5083 welds and 30–80 times shorter for Al 2024 welds than those of sound welds under the stress ratio R = 0.1.
- Published
- 2006
29. Effect of kissing bond on fatigue behavior of friction stir welds on Al 5083 alloy
- Author
-
Caizhi Zhou, Xinqi Yang, and Guohong Luan
- Subjects
Materials science ,Stress ratio ,Mechanical Engineering ,Alloy ,Metallurgy ,engineering.material ,Root tip ,Shear (sheet metal) ,Mechanics of Materials ,engineering ,Fracture (geology) ,General Materials Science ,Friction welding ,Composite material - Abstract
Fatigue properties of FS welds with a kissing bond (bonded welds) were studied by comparing the test results of bonded welds with those of sound welds. The fatigue life of bonded welds is 21∼43 times shorter than that of sound welds under the stress ratio R = 0.1, and the fatigue characteristic values of each welds have decreased from 100.24 MPa for sound welds to 65.57 MPa for bonded welds at 2 × 106 cycles. At the macroscopic level there is no evidence of failure by shear. The fatigue fracture revealed cracks initiated from the root tip of kissing bond.
- Published
- 2006
30. Effect of root flaws on the fatigue property of friction stir welds in 2024-T3 aluminum alloys
- Author
-
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
31. Fatigue properties of friction stir welds in Al 5083 alloy
- Author
-
Xinqi Yang, Caizhi Zhou, and Guohong Luan
- Subjects
Materials science ,Mechanical Engineering ,Alloy ,Metallurgy ,Metals and Alloys ,Welding ,engineering.material ,Condensed Matter Physics ,law.invention ,Gas metal arc welding ,Mechanics of Materials ,law ,engineering ,Friction stir welding ,General Materials Science ,Arc welding ,Friction welding ,Composite material - Abstract
The alloy 5083 was welded by friction stir welding and inert-gas metal-arc welding (MIG-pulse). The fatigue life of friction stir welds is 9–12 times longer than that of MIG-pulse welds under R = 0.1 and the fatigue characteristic values of each welds have been increased from 39.8 MPa for MIG to 67.3 MPa for FSW.
- Published
- 2005
32. Effect of mismatching on J-integral for pipe-welded joints with circumferential through-wall crack
- Author
-
Yueli Liu, Lixing Huo, Xinqi Yang, and Yufeng Zhang
- Subjects
Materials science ,Piping ,Canalisation ,Fissure ,business.industry ,Mechanical Engineering ,Computation ,Numerical analysis ,Welding ,Structural engineering ,Finite element method ,law.invention ,medicine.anatomical_structure ,Mechanics of Materials ,law ,Pure bending ,medicine ,General Materials Science ,business - Abstract
In this article, a J-integral estimation scheme of circumferential through-wall cracked pipe welds under pure bending is introduced. Three-dimensional elasto-plastic finite element computations are carried out, as pipe materials usually have a yielding plateau. Compared with the solution of the finite element method, the results indicate that the LBB.ENG3 scheme is easy to use and can give a satisfactory and reasonable J-integral estimation solution. Finally, the effect of mismatching on the J-integral for pipe-welded joints is discussed in detail.
- Published
- 1999
33. Study on the J-Integral Failure Assessment Curve of Heterogeneous Welded Joints
- Author
-
Xinqi Yang, Li Xing Huo, and You Feng Zhang
- Subjects
J integral ,Materials science ,Mechanics of Materials ,business.industry ,law ,Mechanical Engineering ,General Materials Science ,Structural engineering ,Welding ,business ,Failure assessment ,law.invention - Published
- 1997
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