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
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
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
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
Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding condit...Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.展开更多
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
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
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
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
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
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
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
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
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
Multifunctional flexible sensors as wearable electronic systems have attracted considerable attention for mimicking human skin to sense ambient stimuli.However,sensors need to have high resolution,stability and sensit...Multifunctional flexible sensors as wearable electronic systems have attracted considerable attention for mimicking human skin to sense ambient stimuli.However,sensors need to have high resolution,stability and sensitivity to realize fully biomimetic skin.Here,an assembled and welded Ag/W composite nanowire flexible electrode was prepared for body motion monitoring and flexible heaters.This Ag/W composite nanowire flexible electrode has a high transmittance of 90.1%(at 121Ω·sq^(−1) sheet resistance)and a low sheet resistance of 27Ω·sq^(−1)(at 60.1%transmittance).Although the transparency of this electrode is not high,the fluctuation in relative resistance change rate at 10%strain is only 5%after 1000 tensile cycles.It can be employed to monitor human body motions,including bending of fingers,arms,wrists,and throat action.Meanwhile,the Ag/W nanowires composite film heater achieves a steady-state temperature of up to 100℃ at a constant voltage of 3.5 V and an instantaneous heating rate of up to 36.5℃·s^(−1).展开更多
Welding quality of electron beam welded joint is usually susceptible to the stability of keyhole during welding process.The more stable the keyhole,the better the welding quality.To reveal the evolution mechanism of k...Welding quality of electron beam welded joint is usually susceptible to the stability of keyhole during welding process.The more stable the keyhole,the better the welding quality.To reveal the evolution mechanism of keyhole and welding quality of the electron beam welded joint of magnesium-gadolinium alloy under different scanning path,numerical simulation was conducted for the changes in morphology of keyhole and liquid flow in molten pool.The magnesium-gadolinium alloy was welded by electron beam in vacuum with two different scanning paths,sinusoid path and cochleoid path,indicating the identical heat input,welding speed,and focusing state.The stability of keyhole was mainly related to the frequency of keyhole collapse.When the sinusoid scanning path was adopted,the fluids both inside the molten pool and at keyhole wall were disorder,corresponding to the numerous independent vortices and dramatically chaotic flows at their junctions.The maximum velocity of fluids ranged from 0.79 m/s to 1.02 m/s.The average and maximum depth of keyhole were 3.48 mm and 4.51 mm,respectively,meaning that the keyhole collapsed frequently.As the scanning path was changed into cochleoid mode,the electron beam scanned in a homogeneous manner without abrupt change in direction and speed like sinusoid path at its peaks and troughs.The maximum velocity of fluids was more uniform without drastic variation,ranging from 0.90 m/s to 1.01 m/s.The average and maximum depth of keyhole were decreased to 3.30 mm and 4.05 mm,respectively,indicating the more stable keyhole and alleviated collapse.Both the actual in-situ capture of molten pool signature and porosity inside the weld corresponded to the analysis of the change in keyhole stability.展开更多
This paper focuses on the effect of welding parameters on microstructure and tensile strength of joints welded by friction-stir welding(FSW).The effects of pin profile(threaded conical,non-threaded conical and triangu...This paper focuses on the effect of welding parameters on microstructure and tensile strength of joints welded by friction-stir welding(FSW).The effects of pin profile(threaded conical,non-threaded conical and triangular pin),tool rotational speed(800,1000,1250 and 1600 r·min^(-1))and welding speed(63,80,100 and 125 mm·min^(-1))on the mechanical and microstructural properties of joints welded in 5-mm 7075-T6 were investigated.The results depict that the pin profile has a major role in the shape and grain size of the weld nugget zone(WNZ).In other words,a wider weld nugget and a finer grain size by threaded conical pin are obtained in WNZ.The attained data of tensile tests show that the maximum ultimate tensile strength(UTS)belongs to the threaded conical pin which is attributed to a finer grain size generated in the weld nugget zone.Additionally,it is found that the tensile strength increases with the welding speed increasing,whereas rotational speed has a bilateral effect on the tensile strength.The microhardness tests show that the minimum hardness is obtained in the heat-affected zone(HAZ).展开更多
Insufficient metallurgical compatibility between Zr and Ni can lead to the formation of brittle welds and introduce thermal stress-related challenges during the electron beam welding process.Through the implementation...Insufficient metallurgical compatibility between Zr and Ni can lead to the formation of brittle welds and introduce thermal stress-related challenges during the electron beam welding process.Through the implementation of beam deflection and vibration,a transformation was achieved in the primary Ni_(5)Zr dendrite structure,transitioning from a mass into a layered configuration,consequently resulting in the formation of an ultrafine-grained eutectic−dendrite complex structure.It is revealed that the enhanced strength−ductility synergy of this structure significantly contributes to the high tensile strength and improved plasticity observed in the welded joints.As a result,the welding cracks are effectively mitigated,and notable advancements are achieved in the mechanical properties of Zr/Ni joints,elevating the tensile strength of the joints from 36.4 to 189 MPa.This research not only highlights the potential of this technique in enhancing the strength and ductility of Zr/Ni welded joints but also serves as a valuable reference for future investigations involving welding applications of dissimilar metals.展开更多
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.
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Project (2023GK1080) supported by the Major Special Projects of Hunan Province of China。
文摘Al-Mg-Mn-Sc-Zr alloys with excellent weldability have emerged as ideal candidates for aerospace applications.Currently,the investigations on the corrosion behavior of alloys under tungsten inert gas(TIG)welding conditions are insufficient.Here,the stress corrosion cracking(SCC)behavior of base metal(BM)and weld zone(WZ)of TIG welded Al-Mg-Mn-Sc-Zr alloys was investigated by using pre-cracked compact tensile samples immersed in 3.5%NaCl solution.The direct current potential drop(DCPD)method was used to record the crack propagation.The microstructure and fracture morphology of different regions of TIG welded joints were studied by SEM,EBSD and TEM,and the SCC crack propagation mechanism of BM and WZ was analyzed.The results demonstrated that the critical stress intensity factor for stress corrosion cracking(K_(ⅠSCC))of BM and WZ was 7.05 MPa·m_(1/2) and 11.79 MPa·m_(1/2),respectively.Then,the crack propagation rate of BM was faster than that of WZ,and BM was more susceptible to SCC than WZ.Additionally,the fracture mode of the BM mainly exhibited transgranular fracture,while the fracture mode of the WZ mainly exhibited intergranular and transgranular mixed fracture.Moreover,SCC crack propagation was attributed to the combined effect of anodic dissolution and hydrogen embrittlement.This study will provide experimental and theoretical basis for the wide application of TIG welded Al-Mg-Mn-Sc-Zr alloys in aerospace.
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.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.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.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 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.
基金supported by the National Natural Science Foundation of China(Nos.51905103,52275177).
文摘Multifunctional flexible sensors as wearable electronic systems have attracted considerable attention for mimicking human skin to sense ambient stimuli.However,sensors need to have high resolution,stability and sensitivity to realize fully biomimetic skin.Here,an assembled and welded Ag/W composite nanowire flexible electrode was prepared for body motion monitoring and flexible heaters.This Ag/W composite nanowire flexible electrode has a high transmittance of 90.1%(at 121Ω·sq^(−1) sheet resistance)and a low sheet resistance of 27Ω·sq^(−1)(at 60.1%transmittance).Although the transparency of this electrode is not high,the fluctuation in relative resistance change rate at 10%strain is only 5%after 1000 tensile cycles.It can be employed to monitor human body motions,including bending of fingers,arms,wrists,and throat action.Meanwhile,the Ag/W nanowires composite film heater achieves a steady-state temperature of up to 100℃ at a constant voltage of 3.5 V and an instantaneous heating rate of up to 36.5℃·s^(−1).
基金financially supported by China National Postdoctoral Program for Innovative Talents(BX20230269)National Key R&D Program of China(2022YFB4600800)Fundamental Research Funds for The Central Universities(2042024kf0015).
文摘Welding quality of electron beam welded joint is usually susceptible to the stability of keyhole during welding process.The more stable the keyhole,the better the welding quality.To reveal the evolution mechanism of keyhole and welding quality of the electron beam welded joint of magnesium-gadolinium alloy under different scanning path,numerical simulation was conducted for the changes in morphology of keyhole and liquid flow in molten pool.The magnesium-gadolinium alloy was welded by electron beam in vacuum with two different scanning paths,sinusoid path and cochleoid path,indicating the identical heat input,welding speed,and focusing state.The stability of keyhole was mainly related to the frequency of keyhole collapse.When the sinusoid scanning path was adopted,the fluids both inside the molten pool and at keyhole wall were disorder,corresponding to the numerous independent vortices and dramatically chaotic flows at their junctions.The maximum velocity of fluids ranged from 0.79 m/s to 1.02 m/s.The average and maximum depth of keyhole were 3.48 mm and 4.51 mm,respectively,meaning that the keyhole collapsed frequently.As the scanning path was changed into cochleoid mode,the electron beam scanned in a homogeneous manner without abrupt change in direction and speed like sinusoid path at its peaks and troughs.The maximum velocity of fluids was more uniform without drastic variation,ranging from 0.90 m/s to 1.01 m/s.The average and maximum depth of keyhole were decreased to 3.30 mm and 4.05 mm,respectively,indicating the more stable keyhole and alleviated collapse.Both the actual in-situ capture of molten pool signature and porosity inside the weld corresponded to the analysis of the change in keyhole stability.
文摘This paper focuses on the effect of welding parameters on microstructure and tensile strength of joints welded by friction-stir welding(FSW).The effects of pin profile(threaded conical,non-threaded conical and triangular pin),tool rotational speed(800,1000,1250 and 1600 r·min^(-1))and welding speed(63,80,100 and 125 mm·min^(-1))on the mechanical and microstructural properties of joints welded in 5-mm 7075-T6 were investigated.The results depict that the pin profile has a major role in the shape and grain size of the weld nugget zone(WNZ).In other words,a wider weld nugget and a finer grain size by threaded conical pin are obtained in WNZ.The attained data of tensile tests show that the maximum ultimate tensile strength(UTS)belongs to the threaded conical pin which is attributed to a finer grain size generated in the weld nugget zone.Additionally,it is found that the tensile strength increases with the welding speed increasing,whereas rotational speed has a bilateral effect on the tensile strength.The microhardness tests show that the minimum hardness is obtained in the heat-affected zone(HAZ).
基金supported by the National Natural Science Foundation of China(No.52375322).
文摘Insufficient metallurgical compatibility between Zr and Ni can lead to the formation of brittle welds and introduce thermal stress-related challenges during the electron beam welding process.Through the implementation of beam deflection and vibration,a transformation was achieved in the primary Ni_(5)Zr dendrite structure,transitioning from a mass into a layered configuration,consequently resulting in the formation of an ultrafine-grained eutectic−dendrite complex structure.It is revealed that the enhanced strength−ductility synergy of this structure significantly contributes to the high tensile strength and improved plasticity observed in the welded joints.As a result,the welding cracks are effectively mitigated,and notable advancements are achieved in the mechanical properties of Zr/Ni joints,elevating the tensile strength of the joints from 36.4 to 189 MPa.This research not only highlights the potential of this technique in enhancing the strength and ductility of Zr/Ni welded joints but also serves as a valuable reference for future investigations involving welding applications of dissimilar metals.
