To separately investigate the potential effects of shoulder on increasing interfacial bonded area and its mechanism,friction stir lap welding(FSLW)of 1.8 mm thick Al sheets without and with insert(copper foil or Al-12...To separately investigate the potential effects of shoulder on increasing interfacial bonded area and its mechanism,friction stir lap welding(FSLW)of 1.8 mm thick Al sheets without and with insert(copper foil or Al-12Si powders)was conducted using a special tool without pin,respectively.All the FSLW joints(without insert)fractured within top sheet but not along faying surface,suggesting that the shoulder plays an important role comparable or superior to pin in FSLW of thin sheets.Using several specially designed experimental techniques,the presence of forging and torsion actions of shoulder was demonstrated.The fracture surface of the joints with inserts indicates that interfacial wear occurs,which results in the oxide film disruption and vertically interfacial mixing over the area forged by shoulder with a larger diameter than a general pin,especially at the boundary region of weld.The boundary effect can be induced and enhanced by forging effect and torsion effect.展开更多
Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded aust...Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.展开更多
The friction stir lap welding(FSLW)of metal to polymer is a challenging work due to the unavoidable polymer overflowing.Facing this problem,a novel seal-flow multi-vortex friction stir lap welding(SM-FSLW)technology b...The friction stir lap welding(FSLW)of metal to polymer is a challenging work due to the unavoidable polymer overflowing.Facing this problem,a novel seal-flow multi-vortex friction stir lap welding(SM-FSLW)technology based on the subversively-designed multi-step pin was put forward.Choosing 7075 aluminum alloy and short glass fiber-reinforced polyether ether ketone(PEEK)as research subjects,the welding temperature,material flow,formation and tensile shear strength of dissimilar materials lap joint under the SM-FSLW were studied and compared with those under traditional FSLW based on the conical pin.The multi-step pin rather than the conical pin effectively hindered the polymer overflowing due to the formation of vortexes by the step,thereby attaining a joint with a smooth surface.Compared with traditional FSLW,the SMFSLW obtained the higher welding temperature,the more violent material flow and the larger area with high flow velocity,thereby producing the macro-mechanical and micro-mechanical interlockings and then heightening the joint loading capacity.The tensile shear strength of lap joint under SM-FSLW was 27.8% higher than that under traditional FSLW.The SM-FSLW technology using the multi-step pin provides an effective way on obtaining a heterogeneous lap joint of metal to polymer with the excellent formation and high strength.展开更多
The joining of DP780 steel to Al5052 was conducted by laser lap welding,in which the metal vapor and spatters were monitored by a high-speed camera.A universal testing machine was used to test the mechanical propertie...The joining of DP780 steel to Al5052 was conducted by laser lap welding,in which the metal vapor and spatters were monitored by a high-speed camera.A universal testing machine was used to test the mechanical properties of the welded joints,and the changing law of lap tensile resistance with the laser welding parameters was analyzed.Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure,respectively.Three different intermetallic compounds(IMCs)phases,i.e.banded Fe2Al5,FeAl2 and needle-like FeAl3 were generated at the steel/Al interface on microscopic observation.The aim of this research is to investigate the relationship among the lap tensile resistance,the welding parameters and the failure mode under different energy densities.Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input.The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface,respectively.And both of the two failure modes are brittle fractures.Additionally,cracks appeared at the fracture interface,and needle-like particle clusters were found in the fracture microstructure.展开更多
To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface mi...To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface microstructure and mechanical properties of different FSLW joints were investigated. With increasing the welding speed, the tensile-shear load of FSLW joints produced by three pins presents an increasing firstly and then decreasing trend. Compared with Rpin, the hook and hole defect in the joints made by S-pin and T-pin are eliminated owing to additional eccentric force. Moreover, the joints obtained by T-pin at 75 mm/min have the highest tensile-shear load, and a maximum value of 3.425 kN is produced, which increases by 96.8%.Meanwhile, the pin-tip profile improves significantly the interface reaction depending on the welding temperature. For R-pin, thick brittle intermetallic compounds of about 6.9 μm Al3Mg2and 13.3 μm Al12Mg17layers at the welding interface derived from diffusion reaction are formed, resulting in continuous cracks. However, using T-pin can raise the interface temperature, and which makes the interface liquefy locally to generate only 2.2 μm Al3Mg2layer and dispersive(Al12-Mg17+Mg) eutectic structure. This can release high residual stress and remove welding crack, consequently enhancing the interface properties of T-pin joints.展开更多
The microstructures and lap-shear behaviors of friction stir lap linear welded as-extruded 6061 Al alloy to as-cast Mg–3.0Nd–0.2Zn–0.7Zr(wt.%)(NZ30K)alloy joints were examined.Various tool rotation and travel speed...The microstructures and lap-shear behaviors of friction stir lap linear welded as-extruded 6061 Al alloy to as-cast Mg–3.0Nd–0.2Zn–0.7Zr(wt.%)(NZ30K)alloy joints were examined.Various tool rotation and travel speeds were adopted to prepare the joints.The analysis of temperature field indicates that the peak temperature for each sample can reach 450℃,which exceeds the eutectic reaction temperatures of 437℃ and 450℃ according to the binary phase diagram of Al–Mg system.The fierce intermixing can be found at the interface between Al and Mg alloys,forming the intermetallic of Al_(3)Mg_(2).Welds with the rotation speed of 900 rpm and travel speed of 120 mm/min display the highest tensile shear failure load of about 2.24 kN.The value was increased by 13%after the sample was heat treated at 400℃ for 0.5 h.展开更多
The effect of rotational speed on macro and microstructures, hardness, lap shear performance and failure mode of friction stir lap welding on AA6061-T6 Al alloy with 5 mm in thickness was studied by field-emission sca...The effect of rotational speed on macro and microstructures, hardness, lap shear performance and failure mode of friction stir lap welding on AA6061-T6 Al alloy with 5 mm in thickness was studied by field-emission scanning electron microscopy （FE-SEM）. The results represent much closer hardness distribution in the upper and lower plates at the lowest rotational speed. It indicates the Fe-compounds in the fracture surface of the nugget zone by EDX.展开更多
Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polari...Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polarization, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize corrosion morphology and to realize corrosion mechanism of weld regions as opposed to the parent alloy. The microstructure and shear strength of welded joint were fully investigated. The results indicate that, compared with the parent alloy, the weld regions are susceptible to intergranular and pitting attacks in the test solution during immersion time. The obtained results of lap shear testing disclose that tensile shear strength of the welds is 128 MPa which is more than 60% of the strength of parent alloy in lap shear testing. Electrochemical results show that the protection potentials of the WNZ and HAZ regions are more negative than the pitting potential. This means that the WNZ and HAZ regions do not show more tendencies to pitting corrosion. Corrosion resistance of parent alloy is higher than that for the weldments, and the lowest corrosion resistance is related to the heat affected zone. The pitting attacks originate from the edge of intermetallic particles as the cathode compared with the Al matrix due to their high self-corrosion potential. It is supposed that by increasing intermetallic particle distributed throughout the matrix of weld regions, the galvanic corrosion couples are increased, and hence decrease the corrosion resistance of weld regions.展开更多
文摘To separately investigate the potential effects of shoulder on increasing interfacial bonded area and its mechanism,friction stir lap welding(FSLW)of 1.8 mm thick Al sheets without and with insert(copper foil or Al-12Si powders)was conducted using a special tool without pin,respectively.All the FSLW joints(without insert)fractured within top sheet but not along faying surface,suggesting that the shoulder plays an important role comparable or superior to pin in FSLW of thin sheets.Using several specially designed experimental techniques,the presence of forging and torsion actions of shoulder was demonstrated.The fracture surface of the joints with inserts indicates that interfacial wear occurs,which results in the oxide film disruption and vertically interfacial mixing over the area forged by shoulder with a larger diameter than a general pin,especially at the boundary region of weld.The boundary effect can be induced and enhanced by forging effect and torsion effect.
文摘Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.
基金supported by the National Natural Science Foundation of China(No.52174366)Aeronautical Science Foundation of China(No.2020Z048054002)。
文摘The friction stir lap welding(FSLW)of metal to polymer is a challenging work due to the unavoidable polymer overflowing.Facing this problem,a novel seal-flow multi-vortex friction stir lap welding(SM-FSLW)technology based on the subversively-designed multi-step pin was put forward.Choosing 7075 aluminum alloy and short glass fiber-reinforced polyether ether ketone(PEEK)as research subjects,the welding temperature,material flow,formation and tensile shear strength of dissimilar materials lap joint under the SM-FSLW were studied and compared with those under traditional FSLW based on the conical pin.The multi-step pin rather than the conical pin effectively hindered the polymer overflowing due to the formation of vortexes by the step,thereby attaining a joint with a smooth surface.Compared with traditional FSLW,the SMFSLW obtained the higher welding temperature,the more violent material flow and the larger area with high flow velocity,thereby producing the macro-mechanical and micro-mechanical interlockings and then heightening the joint loading capacity.The tensile shear strength of lap joint under SM-FSLW was 27.8% higher than that under traditional FSLW.The SM-FSLW technology using the multi-step pin provides an effective way on obtaining a heterogeneous lap joint of metal to polymer with the excellent formation and high strength.
基金Project(51675104)supported by the National Natural Science Foundation of ChinaProject(202002020068)supported by the Guangzhou Municipal Special Fund Project for Scientific and Technological Innovation and Development,ChinaProject(2017KCXTD010)supported by the Innovation Team Project,Department of Education of Guangdong Province,China。
文摘The joining of DP780 steel to Al5052 was conducted by laser lap welding,in which the metal vapor and spatters were monitored by a high-speed camera.A universal testing machine was used to test the mechanical properties of the welded joints,and the changing law of lap tensile resistance with the laser welding parameters was analyzed.Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure,respectively.Three different intermetallic compounds(IMCs)phases,i.e.banded Fe2Al5,FeAl2 and needle-like FeAl3 were generated at the steel/Al interface on microscopic observation.The aim of this research is to investigate the relationship among the lap tensile resistance,the welding parameters and the failure mode under different energy densities.Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input.The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface,respectively.And both of the two failure modes are brittle fractures.Additionally,cracks appeared at the fracture interface,and needle-like particle clusters were found in the fracture microstructure.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.52005240 and 52164045)Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province(No.20212BCJ23028)Key Laboratory Fund Project(No.EG202180417).
文摘To improve tensile-shear properties of fiction stir lap welded(FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface microstructure and mechanical properties of different FSLW joints were investigated. With increasing the welding speed, the tensile-shear load of FSLW joints produced by three pins presents an increasing firstly and then decreasing trend. Compared with Rpin, the hook and hole defect in the joints made by S-pin and T-pin are eliminated owing to additional eccentric force. Moreover, the joints obtained by T-pin at 75 mm/min have the highest tensile-shear load, and a maximum value of 3.425 kN is produced, which increases by 96.8%.Meanwhile, the pin-tip profile improves significantly the interface reaction depending on the welding temperature. For R-pin, thick brittle intermetallic compounds of about 6.9 μm Al3Mg2and 13.3 μm Al12Mg17layers at the welding interface derived from diffusion reaction are formed, resulting in continuous cracks. However, using T-pin can raise the interface temperature, and which makes the interface liquefy locally to generate only 2.2 μm Al3Mg2layer and dispersive(Al12-Mg17+Mg) eutectic structure. This can release high residual stress and remove welding crack, consequently enhancing the interface properties of T-pin joints.
基金National Science Foundation of China(No.51401125)Shanghai Pujiang Program(No.15PJ1403200)+1 种基金The Special Fund of Jiangsu Province for the Transformation of Scientific and Technological Achievements(BA2016039)Program of Shanghai Subject Chief Scientists(No.14XD1425000).
文摘The microstructures and lap-shear behaviors of friction stir lap linear welded as-extruded 6061 Al alloy to as-cast Mg–3.0Nd–0.2Zn–0.7Zr(wt.%)(NZ30K)alloy joints were examined.Various tool rotation and travel speeds were adopted to prepare the joints.The analysis of temperature field indicates that the peak temperature for each sample can reach 450℃,which exceeds the eutectic reaction temperatures of 437℃ and 450℃ according to the binary phase diagram of Al–Mg system.The fierce intermixing can be found at the interface between Al and Mg alloys,forming the intermetallic of Al_(3)Mg_(2).Welds with the rotation speed of 900 rpm and travel speed of 120 mm/min display the highest tensile shear failure load of about 2.24 kN.The value was increased by 13%after the sample was heat treated at 400℃ for 0.5 h.
文摘The effect of rotational speed on macro and microstructures, hardness, lap shear performance and failure mode of friction stir lap welding on AA6061-T6 Al alloy with 5 mm in thickness was studied by field-emission scanning electron microscopy （FE-SEM）. The results represent much closer hardness distribution in the upper and lower plates at the lowest rotational speed. It indicates the Fe-compounds in the fracture surface of the nugget zone by EDX.
文摘Corrosion behavior of friction stir lap welded AA6061-T6 aluminum alloy was investigated by immersion tests in sodium chloride + hydrogen peroxide solution. Electrochemical measurement by cyclic potentiodynamic polarization, scanning electron microscopy, and energy dispersive spectroscopy were employed to characterize corrosion morphology and to realize corrosion mechanism of weld regions as opposed to the parent alloy. The microstructure and shear strength of welded joint were fully investigated. The results indicate that, compared with the parent alloy, the weld regions are susceptible to intergranular and pitting attacks in the test solution during immersion time. The obtained results of lap shear testing disclose that tensile shear strength of the welds is 128 MPa which is more than 60% of the strength of parent alloy in lap shear testing. Electrochemical results show that the protection potentials of the WNZ and HAZ regions are more negative than the pitting potential. This means that the WNZ and HAZ regions do not show more tendencies to pitting corrosion. Corrosion resistance of parent alloy is higher than that for the weldments, and the lowest corrosion resistance is related to the heat affected zone. The pitting attacks originate from the edge of intermetallic particles as the cathode compared with the Al matrix due to their high self-corrosion potential. It is supposed that by increasing intermetallic particle distributed throughout the matrix of weld regions, the galvanic corrosion couples are increased, and hence decrease the corrosion resistance of weld regions.
