Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other...Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.展开更多
Friction stir lap welding of AA2195 Al-Li alloy and Ti alloy was conducted to investigate the formation,microstructure,and mechanical properties of the joints.Results show that under different welding parameters,with ...Friction stir lap welding of AA2195 Al-Li alloy and Ti alloy was conducted to investigate the formation,microstructure,and mechanical properties of the joints.Results show that under different welding parameters,with the decrease in welding heat input,the weld surface is smoother.The Ti/Al joint interface is flat without obvious Ti and Al mixed structure,and the hook structure is not formed under optimal parameters.Due to the enhanced breaking effect of the stirring head,the hook structural defects and intermetallic compounds are more likely to form at the Ti/Al interface at high rotational speed of 1000 r/min,thereby deteriorating the mechanical properties of joints.Decreasing the heat input is beneficial to hardness enhancement of the aluminum alloy in the weld nugget zone.Under the optimal parameters of rotation speed of 800 r/min and welding speed of 120 mm/min,the maximum tensile shear strength of joint is 289 N/mm.展开更多
Friction stir welding(FSW)is a relatively new welding technique that has significant advantages compared to the fusion welding techniques in joining non weld able alloys by fusion,such as aluminum alloys.Three FSW sea...Friction stir welding(FSW)is a relatively new welding technique that has significant advantages compared to the fusion welding techniques in joining non weld able alloys by fusion,such as aluminum alloys.Three FSW seams of AA6061-T6 plates were made us-ing different FSW parameters.The structure of the FSW seams was investigated using X-ray diffraction(XRD),scanning electron mi-croscope(SEM)and non destructive testing(NDT)techniques and their hardness was also measured.The dominated phase in the AA6061-T6 alloy and the FSW seams was theα-Al.The FSW seam had lower content of the secondary phases than the AA6061-T6 al-loy.The hardness of the FSW seams was decreased by about 30%compared to the AA6061-T6 alloy.The temperature distributions in the weld seams were also studied experimentally and numerically modeled and the results were in a good agreement.展开更多
Laser twin-arc GTAW(LTA-GTAW)process has been developed by using the synergic interaction effects of laser and a coupled arc in a weld pool to achieve higher energy efficiency.In this study,bead-on-plate welding was c...Laser twin-arc GTAW(LTA-GTAW)process has been developed by using the synergic interaction effects of laser and a coupled arc in a weld pool to achieve higher energy efficiency.In this study,bead-on-plate welding was conducted on 8-mm-thick Q235B work-pieces to investigate the variation of hybrid arc profile,the influence of hybrid arc profile on weld forming,microstructure and mech-anical properties of the joint during the LTA-GTAW process.The influence of Laser-GTAW and LTA-GTAW methods on weld surface appearance,heat input per unit length,and weld metal microstructure were also demonstrated systematically.The LTA-GTAW can make the distribution of arc energy more reasonable in welding depth and width.When defocus is 0,I_(f)is 330 A,I_(b)is 240 A,laser power is 2.4 kW,and spacing between heat sources of tungsten electrode is 10 mm,the weld shape is better.Compared with Laser-GTAW,LTA-GTAW can achieve lower heat input at the same penetration depth,and the microstructure of the weld is refined.The tensile strength of the welded joint is 121.8%of the base material,and the fracture mode of the welded joint is ductile fracture,the comprehensive mechanical properties are better.展开更多
As light metals,aluminum and magnesium have been widely used in automotive manufacturing,but the welding of Al/Mg joints is facing challenges.However,it is difficult to obtain high-quality aluminum/magnesium joints wi...As light metals,aluminum and magnesium have been widely used in automotive manufacturing,but the welding of Al/Mg joints is facing challenges.However,it is difficult to obtain high-quality aluminum/magnesium joints with traditional arc welding methods.As a solid-phase welding technology,ultrasonic metal welding has the characteristics of high welding efficiency and less welded defects.It is also suitable for welding sound metal bonds.Aluminum and magnesium ultrasonic welding has become a research hotspot.Therefore,the evolution of microstructures and mechanical performance of Al/Mg and multi-layer Al/Mg ultrasonic welding,and the new study works,including the molecular dynamic simulation of Al/Mg ultrasonic welding and hybrid based on ultrasonic welding are summarized.Furthermore,several promising research directions are proposed to guide in-depth investigations into the ultrasonic welding of Al/Mg dissimilar joints.展开更多
The composite structures/components made by friction stir lap welding(FSLW)of Mg alloy sheet and Al alloy sheet are of wide application potentials in the manufacturing sector of transportation vehicles.To further impr...The composite structures/components made by friction stir lap welding(FSLW)of Mg alloy sheet and Al alloy sheet are of wide application potentials in the manufacturing sector of transportation vehicles.To further improve the joint quality,the ultrasonic vibration(UV)is exerted in FSLW,and the UV enhanced FSLW(UVeFSLW)was developed for making Mg-to-Al dissimilar joints.The numerical analysis and experimental investigation were combined to study the process mechanism in Mg/Al UVeFSLW.An equation related to the temperature and strain rate was derived to calculate the grain size at different locations of the weld nugget zone,and the effect of grain size distribution on the threshold thermal stress was included,so that the prediction accuracy of flow stress was further improved.With such modified constitutive equation,the numerical simulation was conducted to compare the heat generation,temperature profiles and material flow behaviors in Mg/Al UVeFSLW/FSLW processes.It was found that the exerted UV decreased the temperature at two checking points on the tool/workpiece interface from 707/671 K in FSLW to 689/660 K in UVeFSLW,which suppressed the IMCs thickness at Mg-Al interface from 1.7μm in FSLW to 1.1μm in UVeFSLW.The exerted UV increased the horizontal materials flow ability,and decreased the upward flow ability,which resulted in the increase of effective sheet thickness/effective lap width from 2.01/3.70 mm in FSLW to 2.04/4.84 mm in UVeFSLW.Therefore,the ultrasonic vibration improved the tensile shear strength of Mg-to-Al lap joints by 18%.展开更多
GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 58...GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 582 MPa and 820 MPa,respectively.The HCF strength of joint reaches 400 MPa,which is slightly lower than that of Base Metal(BM),indicating reliable quality of this type of joint.The microstructure observation results show that all cracks initiate at the inside of specimens and transfer into deeper region with decrease of external stress,and the crack initiation site is related with microhardness of matrix.The Electron Backscattered Diffraction(EBSD)results of the observed regions with different distances to fracture show that plastic deformation plays a key role in HCF,and the Schmid factor of most grains near fracture exceeds 0.4.In addition,the generation of twins plays a vital role in strain concentration release and coordinating plastic deformation among grains.展开更多
Tungsten/molybdenum alloys are widely utilized in the nuclear industry,aerospace and various other fields due to their high melting points and strength characteristics.However,poor sinterability and processability mak...Tungsten/molybdenum alloys are widely utilized in the nuclear industry,aerospace and various other fields due to their high melting points and strength characteristics.However,poor sinterability and processability make it difficult to manufacture largesize or complex-shaped parts.Hence,an in-depth study on the welding technology of tungsten/molybdenum alloys is urgent.An introduction of tungsten/molybdenum alloy welding defects and joining process was provided,along with recent advancements in brazing,spark plasma sintering diffusion bonding,electron beam welding and laser beam welding.The latest progress in alloy doping treatment applied to tungsten/molybdenum alloy dissimilar welding was also discussed,and existing welding problems were pointed out.The development prospects of weldability of tungsten/molybdenum alloy by various joining technologies were forecasted,thereby furnishing a theoretical and practical found.展开更多
The study aimed to address the issue of elevated residual stress levels in dissimilar girth welds of cast steel joints.To achieve this,the hybrid welding technology,which yields high welding speeds while simultaneousl...The study aimed to address the issue of elevated residual stress levels in dissimilar girth welds of cast steel joints.To achieve this,the hybrid welding technology,which yields high welding speeds while simultaneously reducing residual stresses,has been introduced.This study utilizes a numerical simulation method to investigate the temperature and residual stress field in the hybrid welding of G20Mn5 casting-Q355 low-alloy steel welded pipe.A com-parison of the findings of this study with those of other welding processes revealed the technological advantages of hybrid welding.The research outcomes show that due to geometric discontinuities and material differences,the temperature field of the joint exhibits uneven distribution characteristics,and the peak temperatures on the Q355 steel side exceeds those on the G20Mn5 steel side.An evident stress gra-dient is present in the residual stress field of the joint post-welding,with peak stress located at the weld root on the Q355 steel.Compared with arc welding,the hybrid welding leads to decreased residual stresses and deformation,with high stress outside the heat-affected zone diminishing rapidly.Furthermore,it significantly improves the welding efficiency.This study elucidates the distribution and underlying causes of thermal and residual stress fields in dissimilar girth welds.This serves as a foundation for the application of hybrid welding technology in welded cast steel joints.展开更多
The steel tube arch rib in a large-span concrete-filled steel tube arch bridge has a large span and diameter,which also leads to a larger weld seam scale.Large-scale welding seams will inevitably cause more obvious we...The steel tube arch rib in a large-span concrete-filled steel tube arch bridge has a large span and diameter,which also leads to a larger weld seam scale.Large-scale welding seams will inevitably cause more obvious welding residual stress(WRS).For the purpose of studying the influence of WRS from large-scale welding seam on the mechanical properties of steel tube arch rib during arch rib splicing,test research and numerical simulation analysis on the WRS in arch rib splicing based on the Guangxi Pingnan Third Bridge,which is the world’s largest span concrete-filled steel tube arch bridge,were conducted in this paper,and the distribution pattern of WRS at the arch rib splicing joint was obtained.Subsequently,the WRS was introduced into the mechanical performance analysis of joints and structures to analyze its effects.The findings reveal that the distribution of WRS in the arch rib is greatly influenced by the rib plate,and the axial WRS in the heat-affected zone are primarily tensile,while the circumferential WRS are distributed in an alternating pattern of tensile and compressive stresses along the circumferential direction of the main tube.Under the influence of WRS,the ultimate bearing capacity of the joint is reduced by 29.4%,the initial axial stiffness is reduced by 4.32%,and the vertical deformation of the arch rib structure is increased by 4.7%.展开更多
Thickness of the intermetallic compounds(IMC)layer at the interface has a significant effect on the mechanical properties of Mg/Al dissimilar joints.However,the thickness of IMC layer can be only obtained by metallurg...Thickness of the intermetallic compounds(IMC)layer at the interface has a significant effect on the mechanical properties of Mg/Al dissimilar joints.However,the thickness of IMC layer can be only obtained by metallurgical microscopy,which is destructive and has to break down the weld.Therefore,it is crucial to find a reliable approach that can non-destructively predict the thickness of IMC layer in practical application.In the current study,Mg alloy and Al alloy were friction stir butt welded(FSW)under different tool rotation speeds(TRS)to obtain different thicknesses of IMC layers.As the TRS increased from 400 rpm to 1000 rpm,thickness of the IMC layer increased from 0.4μm to 1.3μm,the peak welding temperatures increased from 259℃to 402℃,and the Z-axis downforces decreased from10.5 kN to 3.2 k N during welding process.Higher TRS would generally induce higher welding heat input,which promotes the growth of the IMC layer and the softening of base materials.The IMC layer formed through solid-state diffusion and transformation instead of eutectic reaction according to the welding temperature history and interfacial microstructure,and its evolution process was clearly observed by plan view.In order to incorporate the effect of dramatic change of welding temperature which is the characteristic feature of FSW,Psd Voigt function was used to fit the welding temperature histories.A new prediction formula was then established to predict thicknesses of IMC layers with considering sharp welding temperature change.Predicted thicknesses gave good agreement with measured thicknesses obtained experimentally under different welding parameters,which confirmed the accuracy and reliability of the new prediction formula.Based on this prediction formula,the time period of temperature higher than 200℃during welding was found critical for the thickening of interfacial IMC layers.展开更多
High-entropy alloys(HEAs)have become essential materials in the aerospace and defense industries due to their remarkable mechanical properties,which include wear resistance,fatigue endurance,and corrosion resistance.T...High-entropy alloys(HEAs)have become essential materials in the aerospace and defense industries due to their remarkable mechanical properties,which include wear resistance,fatigue endurance,and corrosion resistance.The welding of high-entropy alloys is a cutting-edge field of study that is attracting a lot of interest and investigation from research organizations and businesses.Welding defects including porosity and cracks are challenging problem and limit the development of welding HEAs.This paper provides a comprehensive review of research on weldability of HEAs and the application of diverse welding techniques on welding HEAs over recent years.The forming mechanism and control strategies of defects during welding HEAs were provided in this work.Various welding techniques,including arc welding,laser welding,electron beam welding,friction stir welding,diffusion bonding and explosive welding,have been extensively investigated and applied to improve the microstructure and mechanical properties of HEAs joints.Furthermore,an in-depth review of the microstructure and mechanical properties of HEAs joints obtained by various welding methods is presented.This paper concludes with a discussion of the potential challenges associated with high-entropy alloy welding,thus providing valuable insights for future research efforts in this area.展开更多
A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of ...A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.展开更多
With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as...With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.展开更多
The influence of Ti and Zr,Nb alloying on the microstructures and performance of laser-welded molybdenum socket joints was investigated.Following Nb alloying,the average microhardness of the fusion zone(FZ)increased f...The influence of Ti and Zr,Nb alloying on the microstructures and performance of laser-welded molybdenum socket joints was investigated.Following Nb alloying,the average microhardness of the fusion zone(FZ)increased from HV 194.7 to HV 283.3.Additionally,Nb can react with O to form dispersed Nb_(2)O_(5) along grain boundaries,impeding grain boundary migration and dislocation movement while reducing the content of volatile Mo oxide along these boundaries.The incorporation of Nb in FZ partially inhibits pore defects and enhances joint load-bearing capacity.In comparison to the laser-welded joints without adding Nb(LW),the tensile strength of the laser-welded joints with Nb alloying(LW-Nb)was significantly improved by approximately 69%from 327.5 to 551.7 MPa.Furthermore,the fracture mechanism of the joints transitioned from intergranular fracture to transgranular fracture.展开更多
Owing to process conditions such as uneven clearance of base metal assembly and welding deformation,it is difficult to obtain well-formed structural welds with robot constant specification parameters welding.Determini...Owing to process conditions such as uneven clearance of base metal assembly and welding deformation,it is difficult to obtain well-formed structural welds with robot constant specification parameters welding.Determining how to extract a structured,anti-interference,concise,and dynamic knowledge model from measurable data,and then adjust the welding parameters with corresponding control methods in real time is a central problem to be solved in welding formation control.Hence,this paper proposes a welding penetration control method based on a Neighborhood Rough Set-Adaptive Neuro-Fuzzy Inference System(NRS-ANFIS)to achieve effective penetration control for the GMAW welding process.In orthogonal experiments,the NRS algorithm,which is based on visual sensing to obtain the properties of the weld pool and gap changes,is used to reduce the established frontal weld pool feature information decision table,and the minimum feature set of the weld pool tail width WTand the tail area coefficient CTSis obtained.The minimum feature set of the effective frontal weld pool,real-time line laser distance change,and real-time current information are used as the input for the ANFIS control system.The experimental results for the two groups of time-varying gaps demonstrate that under the condition of no preheating of the base metal,the complete welding penetration rate of the adjusted welding process parameters output by the trained ANFIS model reaches 87%,and the backside melting width is uniform and consistent,which meets the welding specification requirements.展开更多
Welding high-entropy alloy(HEA)to Mg alloy has gained increasing attention for multi-metal structure design,while intrinsic sluggish diffusion kinetics of HEA confines diffusion-controlled interfacial reactions and mak...Welding high-entropy alloy(HEA)to Mg alloy has gained increasing attention for multi-metal structure design,while intrinsic sluggish diffusion kinetics of HEA confines diffusion-controlled interfacial reactions and makes it challenging to establish robust metallurgical bonding.This study investigated welding of FeCoCrNiMn HEA to commercial AZ31 as a model combination to pioneer thisfield.Interfacial phase separation phenomenon was observed,with the diffusion accelerated by in-situ engineering a submicron-scale thick(∼400–500 nm)HEA nearby the interface into nanocrystalline-structure during friction stir welding.Abundant grain boundaries generated in this nanocrystalline-interlayer serve as diffusion short-circuits and energetically preferred nucleation-sites,which promoted Al in AZ31 to diffuse into HEA and triggered quick separation into body-centered cubic AlNi-type and tetragonal FeCr-type intermetallics.HEA and AZ31 were thus metallurgically bonded by these interfacial intermetallics.The joint shows exceptional strength in tensile lap-shear testing with fracture largely occurred within AZ31 rather than right along interface as commonly reported previously for dissimilar joints.展开更多
基金financially supported by the Key Research and Development Program of Ningbo(Grant No.2023Z098)Natural Science Foundation of Inner Mongolia(Grant No.2023MS05040)+1 种基金Shenyang Collaborative Innovation Center Project for Multiple Energy Fields Composite Processing of Special Materials(Grant No.JG210027)Shenyang Key Technology Special Project of The Open Competition Mechanism to Select the Best Solution(Grant Nos.2022210101000827,2022-0-43-048).
文摘Titanium alloy has the advantages of high strength,strong corrosion resistance,excellent high and low temperature mechanical properties,etc.,and is widely used in aerospace,shipbuilding,weapons and equipment,and other fields.In recent years,with the continuous increase in demand for medium-thick plate titanium alloys,corresponding welding technologies have also continued to develop.Therefore,this article reviews the research progress of deep penetration welding technology for medium-thick plate titanium alloys,mainly covering traditional arc welding,high-energy beam welding,and other welding technologies.Among many methods,narrow gap welding,hybrid welding,and external energy field assistance welding all contribute to improving the welding efficiency and quality of medium-thick plate titanium alloys.Finally,the development trend of deep penetration welding technology for mediumthick plate titanium alloys is prospected.
基金National Natural Science Foundation of China(52275349)Key Research and Development Program of Shandong Province(2021ZLGX01)。
文摘Friction stir lap welding of AA2195 Al-Li alloy and Ti alloy was conducted to investigate the formation,microstructure,and mechanical properties of the joints.Results show that under different welding parameters,with the decrease in welding heat input,the weld surface is smoother.The Ti/Al joint interface is flat without obvious Ti and Al mixed structure,and the hook structure is not formed under optimal parameters.Due to the enhanced breaking effect of the stirring head,the hook structural defects and intermetallic compounds are more likely to form at the Ti/Al interface at high rotational speed of 1000 r/min,thereby deteriorating the mechanical properties of joints.Decreasing the heat input is beneficial to hardness enhancement of the aluminum alloy in the weld nugget zone.Under the optimal parameters of rotation speed of 800 r/min and welding speed of 120 mm/min,the maximum tensile shear strength of joint is 289 N/mm.
文摘Friction stir welding(FSW)is a relatively new welding technique that has significant advantages compared to the fusion welding techniques in joining non weld able alloys by fusion,such as aluminum alloys.Three FSW seams of AA6061-T6 plates were made us-ing different FSW parameters.The structure of the FSW seams was investigated using X-ray diffraction(XRD),scanning electron mi-croscope(SEM)and non destructive testing(NDT)techniques and their hardness was also measured.The dominated phase in the AA6061-T6 alloy and the FSW seams was theα-Al.The FSW seam had lower content of the secondary phases than the AA6061-T6 al-loy.The hardness of the FSW seams was decreased by about 30%compared to the AA6061-T6 alloy.The temperature distributions in the weld seams were also studied experimentally and numerically modeled and the results were in a good agreement.
基金supported by the Industrial Innovation Major Technology Global Unveiling Project of Jining City(2022JBZP004)Taishan Scholars Project.
文摘Laser twin-arc GTAW(LTA-GTAW)process has been developed by using the synergic interaction effects of laser and a coupled arc in a weld pool to achieve higher energy efficiency.In this study,bead-on-plate welding was conducted on 8-mm-thick Q235B work-pieces to investigate the variation of hybrid arc profile,the influence of hybrid arc profile on weld forming,microstructure and mech-anical properties of the joint during the LTA-GTAW process.The influence of Laser-GTAW and LTA-GTAW methods on weld surface appearance,heat input per unit length,and weld metal microstructure were also demonstrated systematically.The LTA-GTAW can make the distribution of arc energy more reasonable in welding depth and width.When defocus is 0,I_(f)is 330 A,I_(b)is 240 A,laser power is 2.4 kW,and spacing between heat sources of tungsten electrode is 10 mm,the weld shape is better.Compared with Laser-GTAW,LTA-GTAW can achieve lower heat input at the same penetration depth,and the microstructure of the weld is refined.The tensile strength of the welded joint is 121.8%of the base material,and the fracture mode of the welded joint is ductile fracture,the comprehensive mechanical properties are better.
基金supported by Key Projects of Science and Technology Research Plan of Hubei Provincial Department of Education(D20221306)the National Natural Science Foundation of China(51605103)Key Project of Hubei Provincial Science and Technology Department(2020BAB055).
文摘As light metals,aluminum and magnesium have been widely used in automotive manufacturing,but the welding of Al/Mg joints is facing challenges.However,it is difficult to obtain high-quality aluminum/magnesium joints with traditional arc welding methods.As a solid-phase welding technology,ultrasonic metal welding has the characteristics of high welding efficiency and less welded defects.It is also suitable for welding sound metal bonds.Aluminum and magnesium ultrasonic welding has become a research hotspot.Therefore,the evolution of microstructures and mechanical performance of Al/Mg and multi-layer Al/Mg ultrasonic welding,and the new study works,including the molecular dynamic simulation of Al/Mg ultrasonic welding and hybrid based on ultrasonic welding are summarized.Furthermore,several promising research directions are proposed to guide in-depth investigations into the ultrasonic welding of Al/Mg dissimilar joints.
基金supported by the National Natural Science Foundation of China(Grant No.52035005)the Key R&D Program of Shandong Province in China(Grant No.2021ZLGX01).
文摘The composite structures/components made by friction stir lap welding(FSLW)of Mg alloy sheet and Al alloy sheet are of wide application potentials in the manufacturing sector of transportation vehicles.To further improve the joint quality,the ultrasonic vibration(UV)is exerted in FSLW,and the UV enhanced FSLW(UVeFSLW)was developed for making Mg-to-Al dissimilar joints.The numerical analysis and experimental investigation were combined to study the process mechanism in Mg/Al UVeFSLW.An equation related to the temperature and strain rate was derived to calculate the grain size at different locations of the weld nugget zone,and the effect of grain size distribution on the threshold thermal stress was included,so that the prediction accuracy of flow stress was further improved.With such modified constitutive equation,the numerical simulation was conducted to compare the heat generation,temperature profiles and material flow behaviors in Mg/Al UVeFSLW/FSLW processes.It was found that the exerted UV decreased the temperature at two checking points on the tool/workpiece interface from 707/671 K in FSLW to 689/660 K in UVeFSLW,which suppressed the IMCs thickness at Mg-Al interface from 1.7μm in FSLW to 1.1μm in UVeFSLW.The exerted UV increased the horizontal materials flow ability,and decreased the upward flow ability,which resulted in the increase of effective sheet thickness/effective lap width from 2.01/3.70 mm in FSLW to 2.04/4.84 mm in UVeFSLW.Therefore,the ultrasonic vibration improved the tensile shear strength of Mg-to-Al lap joints by 18%.
基金supported by the National Natural Science Foundation of China(Nos.52074228,52305420,and 51875470)the China Postdoctoral Science Foundation(No.2023M742830)。
文摘GH4169 joints manufactured by Linear Friction Welding(LFW)are subjected to tensile test and stair-case method to evaluate the High Cycle Fatigue(HCF)performance at 650℃.The yield and ultimate tensile strengths are 582 MPa and 820 MPa,respectively.The HCF strength of joint reaches 400 MPa,which is slightly lower than that of Base Metal(BM),indicating reliable quality of this type of joint.The microstructure observation results show that all cracks initiate at the inside of specimens and transfer into deeper region with decrease of external stress,and the crack initiation site is related with microhardness of matrix.The Electron Backscattered Diffraction(EBSD)results of the observed regions with different distances to fracture show that plastic deformation plays a key role in HCF,and the Schmid factor of most grains near fracture exceeds 0.4.In addition,the generation of twins plays a vital role in strain concentration release and coordinating plastic deformation among grains.
基金National Natural Science Foundation of China(52071165,52475347)National Program of Foreign Experts of China(G2023026003L)+4 种基金China Postdoctoral Fund(2023M740475)Program for Science&Technology Innovation Talents in Universities of Henan Province,China(22HASTIT026)Program for the Top Young Talents of Henan Province,China,Frontier Exploration Projects of Longmen Laboratory,China(LMQYTSKT016)Key Scientific Research Projects of Colleges and Universities in Henan Province,China(24A460008)Key Science and Technology Project of Henan Province,China(242102220064,222102230111)。
文摘Tungsten/molybdenum alloys are widely utilized in the nuclear industry,aerospace and various other fields due to their high melting points and strength characteristics.However,poor sinterability and processability make it difficult to manufacture largesize or complex-shaped parts.Hence,an in-depth study on the welding technology of tungsten/molybdenum alloys is urgent.An introduction of tungsten/molybdenum alloy welding defects and joining process was provided,along with recent advancements in brazing,spark plasma sintering diffusion bonding,electron beam welding and laser beam welding.The latest progress in alloy doping treatment applied to tungsten/molybdenum alloy dissimilar welding was also discussed,and existing welding problems were pointed out.The development prospects of weldability of tungsten/molybdenum alloy by various joining technologies were forecasted,thereby furnishing a theoretical and practical found.
基金The SEU Innovation Capability Enhancement Plan for Doctoral Students(No.CXJH_SEU 24115)Marine Economic Development Project of Guangdong Province(No.GDNRC[2022]25).
文摘The study aimed to address the issue of elevated residual stress levels in dissimilar girth welds of cast steel joints.To achieve this,the hybrid welding technology,which yields high welding speeds while simultaneously reducing residual stresses,has been introduced.This study utilizes a numerical simulation method to investigate the temperature and residual stress field in the hybrid welding of G20Mn5 casting-Q355 low-alloy steel welded pipe.A com-parison of the findings of this study with those of other welding processes revealed the technological advantages of hybrid welding.The research outcomes show that due to geometric discontinuities and material differences,the temperature field of the joint exhibits uneven distribution characteristics,and the peak temperatures on the Q355 steel side exceeds those on the G20Mn5 steel side.An evident stress gra-dient is present in the residual stress field of the joint post-welding,with peak stress located at the weld root on the Q355 steel.Compared with arc welding,the hybrid welding leads to decreased residual stresses and deformation,with high stress outside the heat-affected zone diminishing rapidly.Furthermore,it significantly improves the welding efficiency.This study elucidates the distribution and underlying causes of thermal and residual stress fields in dissimilar girth welds.This serves as a foundation for the application of hybrid welding technology in welded cast steel joints.
基金funded by the Science and Technology Research Program of the Chongqing Municipal Education Commission(grant number KJQN202403002).
文摘The steel tube arch rib in a large-span concrete-filled steel tube arch bridge has a large span and diameter,which also leads to a larger weld seam scale.Large-scale welding seams will inevitably cause more obvious welding residual stress(WRS).For the purpose of studying the influence of WRS from large-scale welding seam on the mechanical properties of steel tube arch rib during arch rib splicing,test research and numerical simulation analysis on the WRS in arch rib splicing based on the Guangxi Pingnan Third Bridge,which is the world’s largest span concrete-filled steel tube arch bridge,were conducted in this paper,and the distribution pattern of WRS at the arch rib splicing joint was obtained.Subsequently,the WRS was introduced into the mechanical performance analysis of joints and structures to analyze its effects.The findings reveal that the distribution of WRS in the arch rib is greatly influenced by the rib plate,and the axial WRS in the heat-affected zone are primarily tensile,while the circumferential WRS are distributed in an alternating pattern of tensile and compressive stresses along the circumferential direction of the main tube.Under the influence of WRS,the ultimate bearing capacity of the joint is reduced by 29.4%,the initial axial stiffness is reduced by 4.32%,and the vertical deformation of the arch rib structure is increased by 4.7%.
基金supported by the National Natural Science Foundation of China(No.52075330)the Interdisciplinary Program of Shanghai Jiao Tong University(No.YG2019QNA15)the Foundation of National Facility for Translational Medicine(Shanghai)(No.TMSK-2020-107)。
文摘Thickness of the intermetallic compounds(IMC)layer at the interface has a significant effect on the mechanical properties of Mg/Al dissimilar joints.However,the thickness of IMC layer can be only obtained by metallurgical microscopy,which is destructive and has to break down the weld.Therefore,it is crucial to find a reliable approach that can non-destructively predict the thickness of IMC layer in practical application.In the current study,Mg alloy and Al alloy were friction stir butt welded(FSW)under different tool rotation speeds(TRS)to obtain different thicknesses of IMC layers.As the TRS increased from 400 rpm to 1000 rpm,thickness of the IMC layer increased from 0.4μm to 1.3μm,the peak welding temperatures increased from 259℃to 402℃,and the Z-axis downforces decreased from10.5 kN to 3.2 k N during welding process.Higher TRS would generally induce higher welding heat input,which promotes the growth of the IMC layer and the softening of base materials.The IMC layer formed through solid-state diffusion and transformation instead of eutectic reaction according to the welding temperature history and interfacial microstructure,and its evolution process was clearly observed by plan view.In order to incorporate the effect of dramatic change of welding temperature which is the characteristic feature of FSW,Psd Voigt function was used to fit the welding temperature histories.A new prediction formula was then established to predict thicknesses of IMC layers with considering sharp welding temperature change.Predicted thicknesses gave good agreement with measured thicknesses obtained experimentally under different welding parameters,which confirmed the accuracy and reliability of the new prediction formula.Based on this prediction formula,the time period of temperature higher than 200℃during welding was found critical for the thickening of interfacial IMC layers.
基金Project(52105351)supported by the National Natural Science Foundation of ChinaProject(24KJA460002)supported by the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,ChinaProject(G2023014009L)supported by the High-end Foreign Experts Recruitment Plan of China。
文摘High-entropy alloys(HEAs)have become essential materials in the aerospace and defense industries due to their remarkable mechanical properties,which include wear resistance,fatigue endurance,and corrosion resistance.The welding of high-entropy alloys is a cutting-edge field of study that is attracting a lot of interest and investigation from research organizations and businesses.Welding defects including porosity and cracks are challenging problem and limit the development of welding HEAs.This paper provides a comprehensive review of research on weldability of HEAs and the application of diverse welding techniques on welding HEAs over recent years.The forming mechanism and control strategies of defects during welding HEAs were provided in this work.Various welding techniques,including arc welding,laser welding,electron beam welding,friction stir welding,diffusion bonding and explosive welding,have been extensively investigated and applied to improve the microstructure and mechanical properties of HEAs joints.Furthermore,an in-depth review of the microstructure and mechanical properties of HEAs joints obtained by various welding methods is presented.This paper concludes with a discussion of the potential challenges associated with high-entropy alloy welding,thus providing valuable insights for future research efforts in this area.
基金supported by the National Natural Science Foundation of China(Grant No.52375340,51975263,52405366).
文摘A three-dimensional numerical model of laser-arc hybrid plasma for aluminum alloy fillet joints is developed in this study.This mod-el accounts for the geometric complexity of fillet joints,the physical properties of shielding gases with varying He-Ar ratios,and the coupling between arc plasma and laser-induced metal plume.The accuracy of the model is validated using a high-speed camera.The effects of varying He contents in the shielding gas on both the temperature and flow velocity of hybrid plasma,as well as the distribu-tion of laser-induced metal vapor mass,were investigated separately.The maximum temperature and size of arc plasma decrease as the He volume ratio increases,the arc distribution becomes more concentrated,and its flow velocity initially decreases and then sharply increases.At high helium content,both the flow velocity of hybrid plasma and metal vapor are high,the metal vapor is con-centrated on the right side of keyhole,and its flow appears chaotic.The flow state of arc plasma is most stable when the shielding gas consists of 50%He+50%Ar.
文摘With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.
基金National Key Research and Development Project of China (No. 2022YFB3707602)National Natural Science Foundation of China (Nos. 52005393, 51775416)。
文摘The influence of Ti and Zr,Nb alloying on the microstructures and performance of laser-welded molybdenum socket joints was investigated.Following Nb alloying,the average microhardness of the fusion zone(FZ)increased from HV 194.7 to HV 283.3.Additionally,Nb can react with O to form dispersed Nb_(2)O_(5) along grain boundaries,impeding grain boundary migration and dislocation movement while reducing the content of volatile Mo oxide along these boundaries.The incorporation of Nb in FZ partially inhibits pore defects and enhances joint load-bearing capacity.In comparison to the laser-welded joints without adding Nb(LW),the tensile strength of the laser-welded joints with Nb alloying(LW-Nb)was significantly improved by approximately 69%from 327.5 to 551.7 MPa.Furthermore,the fracture mechanism of the joints transitioned from intergranular fracture to transgranular fracture.
基金Supported by National Natural Science Foundation of China(Grant Nos.52261044,51969001)the Guangxi Provincial Science and Technology Major Project(Grant No.Guike AA23062037)Research Foundation Ability Enhancement Project for Young and Middle Aged Teachers in Guangxi Universities of China(Grant No.2024KY0441)。
文摘Owing to process conditions such as uneven clearance of base metal assembly and welding deformation,it is difficult to obtain well-formed structural welds with robot constant specification parameters welding.Determining how to extract a structured,anti-interference,concise,and dynamic knowledge model from measurable data,and then adjust the welding parameters with corresponding control methods in real time is a central problem to be solved in welding formation control.Hence,this paper proposes a welding penetration control method based on a Neighborhood Rough Set-Adaptive Neuro-Fuzzy Inference System(NRS-ANFIS)to achieve effective penetration control for the GMAW welding process.In orthogonal experiments,the NRS algorithm,which is based on visual sensing to obtain the properties of the weld pool and gap changes,is used to reduce the established frontal weld pool feature information decision table,and the minimum feature set of the weld pool tail width WTand the tail area coefficient CTSis obtained.The minimum feature set of the effective frontal weld pool,real-time line laser distance change,and real-time current information are used as the input for the ANFIS control system.The experimental results for the two groups of time-varying gaps demonstrate that under the condition of no preheating of the base metal,the complete welding penetration rate of the adjusted welding process parameters output by the trained ANFIS model reaches 87%,and the backside melting width is uniform and consistent,which meets the welding specification requirements.
基金supported by the National Natural Science Foundation of China[Grant numbers:52475385,52305392]the China Postdoctoral Science Foundation(Grant No.2022M722048).
文摘Welding high-entropy alloy(HEA)to Mg alloy has gained increasing attention for multi-metal structure design,while intrinsic sluggish diffusion kinetics of HEA confines diffusion-controlled interfacial reactions and makes it challenging to establish robust metallurgical bonding.This study investigated welding of FeCoCrNiMn HEA to commercial AZ31 as a model combination to pioneer thisfield.Interfacial phase separation phenomenon was observed,with the diffusion accelerated by in-situ engineering a submicron-scale thick(∼400–500 nm)HEA nearby the interface into nanocrystalline-structure during friction stir welding.Abundant grain boundaries generated in this nanocrystalline-interlayer serve as diffusion short-circuits and energetically preferred nucleation-sites,which promoted Al in AZ31 to diffuse into HEA and triggered quick separation into body-centered cubic AlNi-type and tetragonal FeCr-type intermetallics.HEA and AZ31 were thus metallurgically bonded by these interfacial intermetallics.The joint shows exceptional strength in tensile lap-shear testing with fracture largely occurred within AZ31 rather than right along interface as commonly reported previously for dissimilar joints.
