Based on the microstructure characterization,electrochemical impedance spectroscopy,potentiodynamic polarization,and immersion corrosion,this work comparatively analyzed the differences in the electrochemical corrosio...Based on the microstructure characterization,electrochemical impedance spectroscopy,potentiodynamic polarization,and immersion corrosion,this work comparatively analyzed the differences in the electrochemical corrosion morphology and post-foil formation surface morphology of laser beam welded(LBW)sample and spin-formed sample,and compared the corrosion resistance and Cu foil formation ability of two samples in H_(2)SO_(4)/NaCl solution and CuSO_(4) reducing electrolyte.Results show that in H_(2)SO_(4) and NaCl solutions,LBW sample and spin-formed sample exhibit excellent passivation ability and corrosion resistance.Both samples show uniform corrosion morphologies and similar corrosion resistance in the strong acidic solution containing Cl^(-).Meanwhile,the Cu foil formation ability of the welded joint is similar to that of the spin-formed sample,and both samples obtain intact Cu foils with high-quality surfaces and small differences in properties.展开更多
Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer ...Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.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
Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can res...Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.展开更多
In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded s...In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.展开更多
The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion...The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion tests and microscopy techniques.Results show that the dissimilar joints exhibit strong stress corrosion cracking(SCC)resistance,maintaining substantial strength during slow strain rate tensile tests.Notably,the heat-affected zone(HAZ)and base metal(BM)on the 6005A+Sc side show superior performance in terms of inter-granular corrosion(IGC)and exfoliation corrosion(EXCO)compared to the corresponding zones on the 5083 side.The lower corrosion resistance of the 5083-BM and the 5083-HAZ can be attributed to the presence of numerous Al_(2)Mg_(3)phases and micro-scaled Al_(6)(Mn,Fe)intermetallics,mainly distributed along the rolling direction.Conversely,the enhanced corrosion resistance of the 6005A+Sc-BM and the 6005A+Sc-HAZ can be attributed to the discontinuously distributed grain boundary precipitates(β-Mg_(2)Si),the smaller grain size,and the reduced corrosive current density.展开更多
7039 Al alloys are widely used in armor vehicles,given the material’s high specific strength and fracture toughness.However,laminar tearing in the thickness plane of the base metal(BM),specifically in the normal dire...7039 Al alloys are widely used in armor vehicles,given the material’s high specific strength and fracture toughness.However,laminar tearing in the thickness plane of the base metal(BM),specifically in the normal direction(ND)and rolling direction(RD)plane,was occasionally observed after the welding of thick plates,resulting in premature material failure.A vertically metal-inert gas(MIG)-welded laminar tearing component of a 30 mm thick plate was analyzed to determine the factors associated with this phenomenon.The texture,residual stress,microhardness,and tensile properties were also investigated.The results indicated that the crack extended along the RD as a transcrystalline fracture and terminated at the BM.The grains near the crack grew preferentially in the(001)crystal direction.Furthermore,the tensile strength(83 MPa)and elongation(6.8%)in the RD were relatively higher than those in the ND.In particular,the primary factors for crack initiation include stronger texture,higher dislocation density,increased Al_(7)Cu_(2)Fe phases,lower proportion of small-angle grain boundaries,and varying grain sizes in different regions,leading to the fragile microstructure.The higher residual stress of the BM promotes the formation and extension of cracks.The restraining force due to fixation and welding shrinkage force transformed the crack into laminar tearing.Preventive measures of laminar tearing were also proposed.展开更多
A low rare-earth containing ZEK100-O magnesium alloy was welded to AA1230-clad high-strength AA2024-T3 aluminum alloy via solidstate ultrasonic spot welding(USW)to evaluate the microstructure,tensile lap shear strengt...A low rare-earth containing ZEK100-O magnesium alloy was welded to AA1230-clad high-strength AA2024-T3 aluminum alloy via solidstate ultrasonic spot welding(USW)to evaluate the microstructure,tensile lap shear strength,and fatigue properties.The tensile strength increased with increasing welding energy,peaked at a welding energy of 1000 J,and then decreased due to the formation of an increasingly thick diffusion layer mainly containing Al12Mg17intermetallic compound at higher energy levels.The peak tensile lap shear strength attained at 1000 J was attributed to the optimal inter-diffusion between the magnesium alloy and softer AA1230-clad Al layer along with the presence of‘fishhook'-like mechanical interlocks at the weld interface and the formation of an indistinguishable intermetallic layer.The dissimilar joints welded at 1000 J also exhibited a longer fatigue life than other Mg-Al dissimilar joints,suggesting the beneficial role of the softer clad layer with a better intermingling capacity during USW.While the transverse-through-thickness(TTT)failure mode prevailed at lower cyclic loading levels,interfacial failure was the predominant mode of fatigue failure at higher cyclic loads,where distinctive fatigue striations were also observed on the fracture surface of the softer clad Al layer.This was associated with the presence of opening stress and bending moment near the nugget edge despite the tension-tension lap shear cyclic loading applied.展开更多
Cu–Ni and Cu–Co–Ni superhydrophobic films were constructed on the surface of B10 copper–nickel alloy welded joints using a two-step process of electrodeposition and stearic acid modification.The chemical compositi...Cu–Ni and Cu–Co–Ni superhydrophobic films were constructed on the surface of B10 copper–nickel alloy welded joints using a two-step process of electrodeposition and stearic acid modification.The chemical composition of the film surface was determined using surface characterization techniques.The corrosion resistance of the films was characterized using electrochemical impedance spectroscopy,potentiodynamic polarization,and scanning Kelvin probe microscopy at multiple scales.The thermal stability,mechanical stability,and self-cleaning properties of the films were also characterized.It was determined that the Cu–Co–Ni superhydrophobic film exhibited the best performance,with a static water contact angle of 159.3°,a roll-off angle of 2.3°,a charge transfer resistance 3300 times higher than the substrate,a self-corrosion current density nearly three orders of magnitude lower,and a surface Kelvin potential increase of 420 mV.The film demonstrated good thermal stability,excellent mechanical stability,and outstanding self-cleaning properties.Combining with previous studies,it was found that Co elements in the film contribute to the formation of a uniform and dense film,Ni elements enhance the adhesion and corrosion resistance between the films,and the combination of Co and Ni elements promotes uniform surface potential and further improves the corrosion resistance and interfilm adhesion of the films.展开更多
The differences between shouldered and shoulderless tools in the micro-friction stir welding of 0.8 mm thin plates were evaluated.Employing a suite of advanced characterization methods,including white light interferom...The differences between shouldered and shoulderless tools in the micro-friction stir welding of 0.8 mm thin plates were evaluated.Employing a suite of advanced characterization methods,including white light interferometry,electron backscatter diffraction(EBSD),and scanning electron microscopy,the formation of weld surface,joint microstructure distribution,and fracture characteristics were studied.The enhancement mechanism of mechanical properties was explained through the Hall-Petch relationship and Taylor's hardening law.Results indicate that the main reason for the increased yield strength observed in shoulderless tool joints is the combined mechanism of dislocation strengthening and fine-grain strengthening.Specifically,the utilization of shouldered tools results in a smooth weld surface,with an average grain size of 11.24μm and a high-angle grain boundary content of 16.80%in the nugget zone.The primary texture components are the{011}<100>Goss and{112}<111>copper textures,yielding a maximum texture strength of 3.70.Simultaneously,the fracture dimples exhibit a reduction in size and an increase in depth.Whereas the welds produced with shoulderless tools display slight burrs on the surface.The experimental results demonstrate that the average grain size in the nugget zone of these joints is significantly reduced to 0.59μm,while the high-angle grain boundary content reaches 34.34%.This process is accompanied by the formation of{111}<110>Shear textures and{001}<110>rotated cubic textures as the main components,resulting in a significant increase in maximum texture strength to 6.65.展开更多
High-performance pure nickel N6/steel 45#composite plate(N6/45#)was prepared using explosive welding technique.The microstructure of the interface and nearby regions was characterized and analyzed by optical microscop...High-performance pure nickel N6/steel 45#composite plate(N6/45#)was prepared using explosive welding technique.The microstructure of the interface and nearby regions was characterized and analyzed by optical microscope,scanning electron microscope,electron backscatter diffraction,and mechanical property testing,and the microstructural features and mechanical properties of the explosive welding interface were explored.The results show that along the direction of explosive welding,the pure nickel N6/steel 45#composite plate interface gradually evolves from a flat bond to a typical wavy bond.The grains at the crests and troughs exhibit high heterogeneity,and the closer to the interface,the finer the grains.Recrystallization and low-stress deformation bands are formed at the bonding interface.Nanoindentation tests reveal that plastic deformation occurs in the interfacial bonding zone,and the nanohardness values in the crest regions are higher than that in the trough regions.The tensile strength of the N6/45#interface is 599.8 MPa,with an average shear strength of 326.3 MPa.No separation phenomenon is observed between N6 and 45#after the bending test.展开更多
Laser beam welding was used to join a near-β titanium alloy(Ti-3Al-6Mo-2Fe-2Zr),followed by aging treatments.The relations among aging temperature,microstructure,and tensile properties of joints were revealed.For as-...Laser beam welding was used to join a near-β titanium alloy(Ti-3Al-6Mo-2Fe-2Zr),followed by aging treatments.The relations among aging temperature,microstructure,and tensile properties of joints were revealed.For as-welded joints,the fusion zone features primarily single β phase.It is attributed to the high Mo equivalency of this alloy and the fast cooling rate in laser beam welding.After aging treatments,many α precipitates form in the fusion zone and heat affected zone.The rising aging temperature coarsens α precipitates and reduces the volume fraction of α precipitates.Compared with the as-welded joints,the aging treated joints'tensile strength and elongation are improved.The increasing aging temperature weakens the strengthening effect because of the decreasing volume fraction of α precipitates.After the aging treatment at 500℃ for 8 h,the joints obtain the optimal match between strength and plasticity.The fracture mode of joints changes from quasi-cleavage fracture in as-welded condition to microvoid coalescence fracture after heat treatments.展开更多
The effect of thermal degradation on the welded hybrid joints of metal and polymer composites is insufficient,which seriously inhibits the engineering applications of the joints.In this study,robust hybrid joints of m...The effect of thermal degradation on the welded hybrid joints of metal and polymer composites is insufficient,which seriously inhibits the engineering applications of the joints.In this study,robust hybrid joints of metal and polymer composites were fabricated by the combination of friction lap welding(FLW)and laser surface treatment for investigating the effect of accelerated aging on the joint properties.Results showed that the FLW hybrid joints without laser surface treatment exhibited 91%reduction in the tensile shear force(TSF)after 7 days of accelerated aging tests.In contrast,the FLW hybrid joints with suitable laser surface treatment exhibited only 26%reduction in TSF even after 35 days of accelerated aging tests.Fractures of the tensile specimens occurred across the composite plates rather than along the joint interface.The enhanced reliability of the hybrid joints was mainly attributed to(1)the formation of micro-mechanical interlocking between the polymer composites and aluminum alloy plate,and(2)the modification of the stress distribution along the joint interface.展开更多
Erratum to:International Journal of Minerals,Metallurgy and Materials Volume 31,Number 11,November 2024,Page 2498 https://doi.org/10.1007/s12613-024-2847-2 In this article,the fund number in the acknowledgements has b...Erratum to:International Journal of Minerals,Metallurgy and Materials Volume 31,Number 11,November 2024,Page 2498 https://doi.org/10.1007/s12613-024-2847-2 In this article,the fund number in the acknowledgements has been erroneously given as the Program for Guangdong Basic and Applied Basic Research Foundation,China(No.2021A151511006)It should be as follows:the Program for Guangdong Basic and Applied Basic Research Foundation,China(No.2021A1515110061).展开更多
This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded(EBW)joint after post weld heat treatment(PWHT)using X-ray diffraction(XRD)and deep-...This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded(EBW)joint after post weld heat treatment(PWHT)using X-ray diffraction(XRD)and deep-hole drilling(DHD)methods,and investigated the microstructure and mechanical properties.During the PWHT at 600℃,a phase transformation(β→α)occurred in the EBW joint and affected the residual stress distribution and mechanical properties.The surface residual stress was mainly compressive stress,while the internal residual stress was mainly tensile stress in the welded joint.For the as-welded joint,the absolute value of surface residual stress was higher than the absolute value of internal residual stress.After PWHT,the residual stress in the treated joint was substantially reduced compared to the as-welded joint,particularly the surface stress,which relieved from−425 to−90 MPa.However,the residual stress relief effect had minimal positive impact on the internal region at 600℃.PWHT resulted in a shift of the joint fracture location from the fusion zone(FZ)to the base metal(BM),and therefore exerted no noticeable effect on the joint strength,but increased the joint elongation significantly.This study provides valuable insights into the regulation of residual stress distribution of ultra-thick titanium alloy plates.展开更多
An alternating magnetic field(AMF)was introduced into the narrow gap laser-arc hybrid welding process for 2205 duplex stainless steel thick plates.The corrosion performance of the welded joints was evaluated through e...An alternating magnetic field(AMF)was introduced into the narrow gap laser-arc hybrid welding process for 2205 duplex stainless steel thick plates.The corrosion performance of the welded joints was evaluated through electrochemical studies.The results revealed that joints welded with the application of AMF had a lower corrosion current density compared to those welded without an external AMF.Additionally,these joints showed higher pitting potential and polarization resistance.Microscopic electrochemical analysis indicated that joints subjected to AMF exhibited minimal cathodic current in simulated seawater,with only slight fluctuations in the anodic current peak.Overall,the corrosion levels on the joint surfaces were relatively low.After 4 h of immersion in the corrosive medium,the average impedance of joints exposed to AMF increased by 60.7%compared to those not influenced by a magnetic field.These findings suggest that applying AMF during the narrow gap laser-arc hybrid welding process can significantly improve the corrosion resistance of duplex stainless steel welded joints,reducing their susceptibility to stress corrosion in seawater-like environments.展开更多
Tungsten inert gas(TIG)welding and laser beam welding(LBW)were employed on as-cast and as-forged Mg−8Li−3Al−2Zn−0.5Y(LAZ832-0.5Y)alloys to investigate their weldability.The microstructure and mechanical properties of ...Tungsten inert gas(TIG)welding and laser beam welding(LBW)were employed on as-cast and as-forged Mg−8Li−3Al−2Zn−0.5Y(LAZ832-0.5Y)alloys to investigate their weldability.The microstructure and mechanical properties of solid solution treated samples were investigated for the purpose of further strength improvement,which were treated at 350℃ for 4 h.The ultimate tensile strength(UTS)and yield strength(YS)of the optimal TIG as-cast alloy welding joint were 159 and 122 MPa,which were obtained under the welding current of 80 A,and were lower than the UTS(184 MPa)and YS(146 MPa)of the optimal LBW as-forged welding joint under the power of 2.1 kW/2.0 kW double-side welding.After the solid solution treatment,on the one hand,the growth ofα-Mg grains in the fusion zone(FZ),heat affected zone(HAZ)and base metal(BM)of both the TIG and LBW welding joints was insignificant.On the other hand,the larger Al_(2)Y phases were still present,while the much smaller white AlLi particles were dissolved into the matrix,leading to the solid solution strengthening of the welding joints.As a result,the UTS and YS of the TIG welding joint respectively increased to 216 and 188 MPa after solid solution treatment,and those of the LBW welding joint only increased to 211 and 160 MPa,respectively.展开更多
Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively invest...Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.展开更多
The 7075 aluminum alloy was subjected to power-modulated laser welding using a full-domain power modulation(FDPM)laser oscillating welding system.Three different power modes were utilized:constant power(CP),gradient p...The 7075 aluminum alloy was subjected to power-modulated laser welding using a full-domain power modulation(FDPM)laser oscillating welding system.Three different power modes were utilized:constant power(CP),gradient power(GP),and alternating power(AP)modes.The impact of different power modes on joint crack sensitivity,microstructure,and residual stress was assessed.The results demonstrate that joint welded with the AP mode exhibits the lowest sensitivity to solidification cracking(with mean crack sensitivity of 18.3%),and the smallest average grain size in the fusion zone of the weld seam(80μm).Additionally,it shows the highest microhardness(HV 113)and the narrowest softening region(3.5 cm).Furthermore,the joint displays the lowest residual stress and cooling rate,which is the reason for its minimal crack sensitivity.展开更多
The corrosion behavior of the tungsten inert gas(TIG)welded Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy with different post-weld heat treatments was systematically investigated.The results show that the corrosion resistance of the s...The corrosion behavior of the tungsten inert gas(TIG)welded Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy with different post-weld heat treatments was systematically investigated.The results show that the corrosion resistance of the sand-cast base material(BM)was inferior to that of the fusion zone(FZ),which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg_3(Nd,Gd)eutectic phases and numerousβprecipitates.It is found that post-weld solid-solution(T4)treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution.The precipitation of nanosized phases and Zn-Zr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged(T6) joint.As the main corrosion products,MgO and Mg(OH)_(2) are distributed throughout the whole corrosion film,while RE oxides and RE hydroxides are mainly distributed in the inner layer,which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)_(2).Based on the composition and structure of the corrosion product film,a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints.This work could promote the applications of welded Mg-RE alloy joint in some corrosion environments.展开更多
基金Key Research and Development Program of Shaanxi Province(2022GY-410)Funding of Western Titanium Technologies Co.,Ltd(WX2210)。
文摘Based on the microstructure characterization,electrochemical impedance spectroscopy,potentiodynamic polarization,and immersion corrosion,this work comparatively analyzed the differences in the electrochemical corrosion morphology and post-foil formation surface morphology of laser beam welded(LBW)sample and spin-formed sample,and compared the corrosion resistance and Cu foil formation ability of two samples in H_(2)SO_(4)/NaCl solution and CuSO_(4) reducing electrolyte.Results show that in H_(2)SO_(4) and NaCl solutions,LBW sample and spin-formed sample exhibit excellent passivation ability and corrosion resistance.Both samples show uniform corrosion morphologies and similar corrosion resistance in the strong acidic solution containing Cl^(-).Meanwhile,the Cu foil formation ability of the welded joint is similar to that of the spin-formed sample,and both samples obtain intact Cu foils with high-quality surfaces and small differences in properties.
基金Opening Foundation of Key Laboratory of Explosive Energy Utilization and Control,Anhui Province(BP20240104)Graduate Innovation Program of China University of Mining and Technology(2024WLJCRCZL049)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX24_2701)。
文摘Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.
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supported by the National Natural Science Foundation of China(No.51871155).
文摘Due to the low content of alloying elements and the lack of effective nucleation sites,the fusion zone(FZ)of tungsten inert gas(TIG)welded AZ31 alloy typically exhibits undesirable coarse columnar grains,which can result in solidification defects and reduced mechanical properties.In this work,a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition(CET)in the FZ of TIG-welded AZ31 alloy.The results show the achievement of a fully equiaxed grain structure in the FZ,with a significant 71.9%reduction in grain size to 41 μm from the original coarse columnar dendrites.Furthermore,the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm.Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ.The application of pulse current results in an increase in the number density of MgO(1-2 μm)from 5.16 × 10^(4) m^(-3) to 6.18 × 10^(4) m^(-3).The good crystallographic matching relationship between MgO and α-Mg matrix,characterized by the orientation relationship of[11(2)0]α-Mg//[0(1)1]MgO and(0002)_(α-Mg)//(111)_(MgO),indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling.According to the Hunt criteria,the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites.In addition,the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map,leading to the realization of CET.The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints.This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.
基金Funded by the National Natural Science Foundation of China(Nos.52075347,51575364)and the Natural Science Foundation of Liaoning Provincial(No.2022-MS-295)。
文摘In order to solve the problem of poor formability caused by different materials and properties in the process of tailor-welded sheets forming,a forming method was proposed to change the stress state of tailor-welded sheets by covering the tailor-welded sheets with better plastic properties overlapping sheets.At the same time,the interface friction effect between the overlapping and tailor-welded sheets was utilized to control the stress magnitude and further improve the formability and quality of the tailor-welded sheets.In this work,the bulging process of the tailor-welded overlapping sheets was taken as the research object.Aluminum alloy tailor-welded overlapping sheets bulging specimens were studied by a combination of finite element analysis and experimental verification.The results show that the appropriate use of interface friction between tailor-welded and overlapping sheets can improve the formability of tailor-welded sheets and control the flow of weld seam to improve the forming quality.When increasing the interface friction coefficient on the side of tailor-welded sheets with higher strength and decreasing that on the side of tailor-welded sheets with lower strength,the deformation of the tailor-welded sheets are more uniform,the offset of the weld seam is minimal,the limit bulging height is maximal,and the forming quality is optimal.
基金financially supported by the Science and Technology Innovation Program of Hunan Province,China(No.2023RC3055)the Natural Science Foundation of Hunan Province,China(Nos.2023JJ30671,2020JJ4114)+5 种基金the Natural Science Foundation of Changsha City,China(No.Kq2208264)National Key Project of Research and Development Plan of China(Nos.2021YFC1910505,2021YFC1910504)the Young Core Teacher Foundation of Hunan Province,China(No.150220001)Key Research and Development Program of Guangdong Province,China(No.2020B010186002)the National Natural Science Foundation of China(No.51601229)the Key-Area Research and Development Program of Foshan City,China(No.2230032004640).
文摘The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion tests and microscopy techniques.Results show that the dissimilar joints exhibit strong stress corrosion cracking(SCC)resistance,maintaining substantial strength during slow strain rate tensile tests.Notably,the heat-affected zone(HAZ)and base metal(BM)on the 6005A+Sc side show superior performance in terms of inter-granular corrosion(IGC)and exfoliation corrosion(EXCO)compared to the corresponding zones on the 5083 side.The lower corrosion resistance of the 5083-BM and the 5083-HAZ can be attributed to the presence of numerous Al_(2)Mg_(3)phases and micro-scaled Al_(6)(Mn,Fe)intermetallics,mainly distributed along the rolling direction.Conversely,the enhanced corrosion resistance of the 6005A+Sc-BM and the 6005A+Sc-HAZ can be attributed to the discontinuously distributed grain boundary precipitates(β-Mg_(2)Si),the smaller grain size,and the reduced corrosive current density.
基金supported by the National Key Research and Development Program of China(No.SQ2021YFF 0600011).
文摘7039 Al alloys are widely used in armor vehicles,given the material’s high specific strength and fracture toughness.However,laminar tearing in the thickness plane of the base metal(BM),specifically in the normal direction(ND)and rolling direction(RD)plane,was occasionally observed after the welding of thick plates,resulting in premature material failure.A vertically metal-inert gas(MIG)-welded laminar tearing component of a 30 mm thick plate was analyzed to determine the factors associated with this phenomenon.The texture,residual stress,microhardness,and tensile properties were also investigated.The results indicated that the crack extended along the RD as a transcrystalline fracture and terminated at the BM.The grains near the crack grew preferentially in the(001)crystal direction.Furthermore,the tensile strength(83 MPa)and elongation(6.8%)in the RD were relatively higher than those in the ND.In particular,the primary factors for crack initiation include stronger texture,higher dislocation density,increased Al_(7)Cu_(2)Fe phases,lower proportion of small-angle grain boundaries,and varying grain sizes in different regions,leading to the fragile microstructure.The higher residual stress of the BM promotes the formation and extension of cracks.The restraining force due to fixation and welding shrinkage force transformed the crack into laminar tearing.Preventive measures of laminar tearing were also proposed.
基金the National Natural Science Foundation of China(Grant No.51971183)supported by OU(Osaka University,Japan)program for multilateral international collaboration research in joining and welding。
文摘A low rare-earth containing ZEK100-O magnesium alloy was welded to AA1230-clad high-strength AA2024-T3 aluminum alloy via solidstate ultrasonic spot welding(USW)to evaluate the microstructure,tensile lap shear strength,and fatigue properties.The tensile strength increased with increasing welding energy,peaked at a welding energy of 1000 J,and then decreased due to the formation of an increasingly thick diffusion layer mainly containing Al12Mg17intermetallic compound at higher energy levels.The peak tensile lap shear strength attained at 1000 J was attributed to the optimal inter-diffusion between the magnesium alloy and softer AA1230-clad Al layer along with the presence of‘fishhook'-like mechanical interlocks at the weld interface and the formation of an indistinguishable intermetallic layer.The dissimilar joints welded at 1000 J also exhibited a longer fatigue life than other Mg-Al dissimilar joints,suggesting the beneficial role of the softer clad layer with a better intermingling capacity during USW.While the transverse-through-thickness(TTT)failure mode prevailed at lower cyclic loading levels,interfacial failure was the predominant mode of fatigue failure at higher cyclic loads,where distinctive fatigue striations were also observed on the fracture surface of the softer clad Al layer.This was associated with the presence of opening stress and bending moment near the nugget edge despite the tension-tension lap shear cyclic loading applied.
基金fnancial support by the National Natural Science Foundation of China(Grant No.42176209)the Natural Science Foundation of Shandong Province(Grant No.ZR2021MD064).
文摘Cu–Ni and Cu–Co–Ni superhydrophobic films were constructed on the surface of B10 copper–nickel alloy welded joints using a two-step process of electrodeposition and stearic acid modification.The chemical composition of the film surface was determined using surface characterization techniques.The corrosion resistance of the films was characterized using electrochemical impedance spectroscopy,potentiodynamic polarization,and scanning Kelvin probe microscopy at multiple scales.The thermal stability,mechanical stability,and self-cleaning properties of the films were also characterized.It was determined that the Cu–Co–Ni superhydrophobic film exhibited the best performance,with a static water contact angle of 159.3°,a roll-off angle of 2.3°,a charge transfer resistance 3300 times higher than the substrate,a self-corrosion current density nearly three orders of magnitude lower,and a surface Kelvin potential increase of 420 mV.The film demonstrated good thermal stability,excellent mechanical stability,and outstanding self-cleaning properties.Combining with previous studies,it was found that Co elements in the film contribute to the formation of a uniform and dense film,Ni elements enhance the adhesion and corrosion resistance between the films,and the combination of Co and Ni elements promotes uniform surface potential and further improves the corrosion resistance and interfilm adhesion of the films.
基金National Nature Science Foundation of China(52261013)。
文摘The differences between shouldered and shoulderless tools in the micro-friction stir welding of 0.8 mm thin plates were evaluated.Employing a suite of advanced characterization methods,including white light interferometry,electron backscatter diffraction(EBSD),and scanning electron microscopy,the formation of weld surface,joint microstructure distribution,and fracture characteristics were studied.The enhancement mechanism of mechanical properties was explained through the Hall-Petch relationship and Taylor's hardening law.Results indicate that the main reason for the increased yield strength observed in shoulderless tool joints is the combined mechanism of dislocation strengthening and fine-grain strengthening.Specifically,the utilization of shouldered tools results in a smooth weld surface,with an average grain size of 11.24μm and a high-angle grain boundary content of 16.80%in the nugget zone.The primary texture components are the{011}<100>Goss and{112}<111>copper textures,yielding a maximum texture strength of 3.70.Simultaneously,the fracture dimples exhibit a reduction in size and an increase in depth.Whereas the welds produced with shoulderless tools display slight burrs on the surface.The experimental results demonstrate that the average grain size in the nugget zone of these joints is significantly reduced to 0.59μm,while the high-angle grain boundary content reaches 34.34%.This process is accompanied by the formation of{111}<110>Shear textures and{001}<110>rotated cubic textures as the main components,resulting in a significant increase in maximum texture strength to 6.65.
基金Natural Science Foundation of Shanxi Province(202203021221149)Key Research and Development Program of Shanxi Province(202302010101006,202202150401016)+1 种基金Scientific Research Start-up Fund for the Introduction of Talents in Shanxi Institute of Electronic Science and Technology(2023RKJ021)Key R&D Program of Linfen City(2334)。
文摘High-performance pure nickel N6/steel 45#composite plate(N6/45#)was prepared using explosive welding technique.The microstructure of the interface and nearby regions was characterized and analyzed by optical microscope,scanning electron microscope,electron backscatter diffraction,and mechanical property testing,and the microstructural features and mechanical properties of the explosive welding interface were explored.The results show that along the direction of explosive welding,the pure nickel N6/steel 45#composite plate interface gradually evolves from a flat bond to a typical wavy bond.The grains at the crests and troughs exhibit high heterogeneity,and the closer to the interface,the finer the grains.Recrystallization and low-stress deformation bands are formed at the bonding interface.Nanoindentation tests reveal that plastic deformation occurs in the interfacial bonding zone,and the nanohardness values in the crest regions are higher than that in the trough regions.The tensile strength of the N6/45#interface is 599.8 MPa,with an average shear strength of 326.3 MPa.No separation phenomenon is observed between N6 and 45#after the bending test.
基金National Natural Science Foundation of China(51804097)Fundamental Research Funds for the Central Universities of China(B220202026)Changzhou Sci&Tech Program(CJ20220074)。
文摘Laser beam welding was used to join a near-β titanium alloy(Ti-3Al-6Mo-2Fe-2Zr),followed by aging treatments.The relations among aging temperature,microstructure,and tensile properties of joints were revealed.For as-welded joints,the fusion zone features primarily single β phase.It is attributed to the high Mo equivalency of this alloy and the fast cooling rate in laser beam welding.After aging treatments,many α precipitates form in the fusion zone and heat affected zone.The rising aging temperature coarsens α precipitates and reduces the volume fraction of α precipitates.Compared with the as-welded joints,the aging treated joints'tensile strength and elongation are improved.The increasing aging temperature weakens the strengthening effect because of the decreasing volume fraction of α precipitates.After the aging treatment at 500℃ for 8 h,the joints obtain the optimal match between strength and plasticity.The fracture mode of joints changes from quasi-cleavage fracture in as-welded condition to microvoid coalescence fracture after heat treatments.
基金supported by the National Natural Science Foundation of China(No.51975553)the Liaoning Natural Science Foundation of China(Nos.2021-MS-007 and 2021-YQ-01)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193).
文摘The effect of thermal degradation on the welded hybrid joints of metal and polymer composites is insufficient,which seriously inhibits the engineering applications of the joints.In this study,robust hybrid joints of metal and polymer composites were fabricated by the combination of friction lap welding(FLW)and laser surface treatment for investigating the effect of accelerated aging on the joint properties.Results showed that the FLW hybrid joints without laser surface treatment exhibited 91%reduction in the tensile shear force(TSF)after 7 days of accelerated aging tests.In contrast,the FLW hybrid joints with suitable laser surface treatment exhibited only 26%reduction in TSF even after 35 days of accelerated aging tests.Fractures of the tensile specimens occurred across the composite plates rather than along the joint interface.The enhanced reliability of the hybrid joints was mainly attributed to(1)the formation of micro-mechanical interlocking between the polymer composites and aluminum alloy plate,and(2)the modification of the stress distribution along the joint interface.
文摘Erratum to:International Journal of Minerals,Metallurgy and Materials Volume 31,Number 11,November 2024,Page 2498 https://doi.org/10.1007/s12613-024-2847-2 In this article,the fund number in the acknowledgements has been erroneously given as the Program for Guangdong Basic and Applied Basic Research Foundation,China(No.2021A151511006)It should be as follows:the Program for Guangdong Basic and Applied Basic Research Foundation,China(No.2021A1515110061).
基金supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2021193)the Science and Technology Cooperation Project between Jilin Province and Chinese Academy of Sciences(No.2024SYHZ0032).
文摘This study analyzed through-thickness distribution of residual stress in a 106 mm ultra-thick TC4 titanium alloy electron beam welded(EBW)joint after post weld heat treatment(PWHT)using X-ray diffraction(XRD)and deep-hole drilling(DHD)methods,and investigated the microstructure and mechanical properties.During the PWHT at 600℃,a phase transformation(β→α)occurred in the EBW joint and affected the residual stress distribution and mechanical properties.The surface residual stress was mainly compressive stress,while the internal residual stress was mainly tensile stress in the welded joint.For the as-welded joint,the absolute value of surface residual stress was higher than the absolute value of internal residual stress.After PWHT,the residual stress in the treated joint was substantially reduced compared to the as-welded joint,particularly the surface stress,which relieved from−425 to−90 MPa.However,the residual stress relief effect had minimal positive impact on the internal region at 600℃.PWHT resulted in a shift of the joint fracture location from the fusion zone(FZ)to the base metal(BM),and therefore exerted no noticeable effect on the joint strength,but increased the joint elongation significantly.This study provides valuable insights into the regulation of residual stress distribution of ultra-thick titanium alloy plates.
基金supported by the National Natural Science Foundation of China(No.52265054)the Inner Mongolia Autonomous Region Natural Science Foundation Project(No.2022ZD03)+3 种基金the Inner Mongolia Autonomous Region Science and Technology Plan Project(No.2020GG0313)the Inner Mongolia Autonomous Region Natural Science Foundation Doctoral Fund Project,(No.2021BS05016)the Construction project of integrated research and development platform for key technologies in the development and processing of new nonferrous metal materials(No.RZ2300001971)the Basic Research Business Fee Project for Autonomous Region Directly Affiliated Universities(Nos.JY20220199 and JY20220028).
文摘An alternating magnetic field(AMF)was introduced into the narrow gap laser-arc hybrid welding process for 2205 duplex stainless steel thick plates.The corrosion performance of the welded joints was evaluated through electrochemical studies.The results revealed that joints welded with the application of AMF had a lower corrosion current density compared to those welded without an external AMF.Additionally,these joints showed higher pitting potential and polarization resistance.Microscopic electrochemical analysis indicated that joints subjected to AMF exhibited minimal cathodic current in simulated seawater,with only slight fluctuations in the anodic current peak.Overall,the corrosion levels on the joint surfaces were relatively low.After 4 h of immersion in the corrosive medium,the average impedance of joints exposed to AMF increased by 60.7%compared to those not influenced by a magnetic field.These findings suggest that applying AMF during the narrow gap laser-arc hybrid welding process can significantly improve the corrosion resistance of duplex stainless steel welded joints,reducing their susceptibility to stress corrosion in seawater-like environments.
基金supported by the National Defense Basic Research Program of China(No.JCKY2023204A005)the Research Program of Joint Research Center of Advanced Spaceflight Technologies of China(No.USCAST2023-3)+2 种基金the National Natural Science Foundation of China(No.U2037601)the Major Scientific and Technological Innovation Project of Luoyang,Henan Province,China(No.2201029A)the Foundation Strengthening Plan Technical Field Fund,China(No.2021-JJ-0112).
文摘Tungsten inert gas(TIG)welding and laser beam welding(LBW)were employed on as-cast and as-forged Mg−8Li−3Al−2Zn−0.5Y(LAZ832-0.5Y)alloys to investigate their weldability.The microstructure and mechanical properties of solid solution treated samples were investigated for the purpose of further strength improvement,which were treated at 350℃ for 4 h.The ultimate tensile strength(UTS)and yield strength(YS)of the optimal TIG as-cast alloy welding joint were 159 and 122 MPa,which were obtained under the welding current of 80 A,and were lower than the UTS(184 MPa)and YS(146 MPa)of the optimal LBW as-forged welding joint under the power of 2.1 kW/2.0 kW double-side welding.After the solid solution treatment,on the one hand,the growth ofα-Mg grains in the fusion zone(FZ),heat affected zone(HAZ)and base metal(BM)of both the TIG and LBW welding joints was insignificant.On the other hand,the larger Al_(2)Y phases were still present,while the much smaller white AlLi particles were dissolved into the matrix,leading to the solid solution strengthening of the welding joints.As a result,the UTS and YS of the TIG welding joint respectively increased to 216 and 188 MPa after solid solution treatment,and those of the LBW welding joint only increased to 211 and 160 MPa,respectively.
文摘Dissimilar AZ31B magnesium alloy and DC56D steel were welded via AA1060 aluminum alloy by magnetic pulse welding.The effects of primary and secondary welding processes on the welded interface were comparatively investigated.Macroscopic morphology,microstructure,and interfacial structure of the joints were analyzed using scanning electron microscope,energy dispersive spectrometer,and X-ray diffractometer(XRD).The results show that magnetic pulse welding of dissimilar Mg/Fe metals is achieved using an Al interlayer,which acts as a bridge for deformation and diffusion.Specifically,the AZ31B/AA1060 interface exhibits a typical wavy morphology,and a transition zone exists at the joint interface,which may result in an extremely complex microstructure.The microstructure of this transition zone differs from that of AZ31B magnesium and 1060 Al alloys,and it is identified as brittle intermetallic compounds(IMCs)Al_(3)Mg_(2) and Al_(12)Mg_(17).The transition zone is mainly distributed on the Al side,with the maximum thickness of Al-side transition layer reaching approximately 13.53μm.Incomplete melting layers with varying thicknesses are observed at the primary weld interface,while micron-sized hole defects appear in the transition zone of the secondary weld interface.The AA1060/DC56D interface is mainly straight,with only a small number of discontinuous transition zones distributed intermittently along the interface.These transition zones are characterized by the presence of the brittle IMC FeAl_(3),with a maximum thickness of about 4μm.
基金supported by the National Natural Science Foundation of China(No.52075235)the Major Science and Technology Project of Gansu Province,China(No.22ZD6GA008)+2 种基金the Key Research and Development Program of Gansu Province,China(No.20YF3WA017)the Natural Science Foundation of Gansu Province,China(No.21JR7RA233)the Scientific and Technological Projects of Jiayuguan,China(No.22-16)。
文摘The 7075 aluminum alloy was subjected to power-modulated laser welding using a full-domain power modulation(FDPM)laser oscillating welding system.Three different power modes were utilized:constant power(CP),gradient power(GP),and alternating power(AP)modes.The impact of different power modes on joint crack sensitivity,microstructure,and residual stress was assessed.The results demonstrate that joint welded with the AP mode exhibits the lowest sensitivity to solidification cracking(with mean crack sensitivity of 18.3%),and the smallest average grain size in the fusion zone of the weld seam(80μm).Additionally,it shows the highest microhardness(HV 113)and the narrowest softening region(3.5 cm).Furthermore,the joint displays the lowest residual stress and cooling rate,which is the reason for its minimal crack sensitivity.
基金supported by the National Natural Science Foundation of China(Nos.U2037601,U2241231,and 51821001)。
文摘The corrosion behavior of the tungsten inert gas(TIG)welded Mg-3Nd-3Gd-0.2Zn-0.5Zr alloy with different post-weld heat treatments was systematically investigated.The results show that the corrosion resistance of the sand-cast base material(BM)was inferior to that of the fusion zone(FZ),which was attributed to the larger grain size and exacerbated galvanic corrosion caused by coarser Mg_3(Nd,Gd)eutectic phases and numerousβprecipitates.It is found that post-weld solid-solution(T4)treatment could significantly enhance the corrosion resistance of the joint due to the dissolution of the cathodic second phases and the denser protective film abundant in RE oxides generated in corrosive solution.The precipitation of nanosized phases and Zn-Zr clusters would slightly increase the susceptibility to localized corrosion of the peak-aged(T6) joint.As the main corrosion products,MgO and Mg(OH)_(2) are distributed throughout the whole corrosion film,while RE oxides and RE hydroxides are mainly distributed in the inner layer,which can be explained by inward oxidation and replacement reactions between RE elements and MgO/Mg(OH)_(2).Based on the composition and structure of the corrosion product film,a physical model has been proposed for depicting the microstructure evolution associated with the corresponding corrosion behavior of the joints.This work could promote the applications of welded Mg-RE alloy joint in some corrosion environments.
