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
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
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
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
Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool...Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool tilt angle.FSW parameters significantly affect the weld strength.Tool tilt angle is one of the significant process parameters among the weld parameters.The present study focused on the effect of tool tilt angle on strength of friction stir lap welding of AA2014-T6 aluminium alloy.The tool tilt angle was varied between 0°and 4°with an equal increment of 1°.Other process parameters were kept constant.Macrostructure and microstructure analysis,microhardness measurement,scanning electron micrograph,transmission electron micrograph and energy dispersive spectroscopy analysis were performed to evaluate the lap shear strength of friction stir lap welded joint.Results proved that,defect-free weld joint was obtained while using a tool tilt angle of 1°to 3°.However,sound joints were welded using a tool tilt angle of 2°,which had the maximum lap shear strength of 14.42 kN and microhardness of HV 132.The joints welded using tool tilt angles of 1°and 3°yielded inferior lap shear strength due to unbalanced material flow in the weld region during FSW.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
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.
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.
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.
基金Aeronautical Development Agency (ADA), Bangalore, India, for the financial support to carry out this investigation through an R&D project No: FSED 83.07.03
文摘Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool tilt angle.FSW parameters significantly affect the weld strength.Tool tilt angle is one of the significant process parameters among the weld parameters.The present study focused on the effect of tool tilt angle on strength of friction stir lap welding of AA2014-T6 aluminium alloy.The tool tilt angle was varied between 0°and 4°with an equal increment of 1°.Other process parameters were kept constant.Macrostructure and microstructure analysis,microhardness measurement,scanning electron micrograph,transmission electron micrograph and energy dispersive spectroscopy analysis were performed to evaluate the lap shear strength of friction stir lap welded joint.Results proved that,defect-free weld joint was obtained while using a tool tilt angle of 1°to 3°.However,sound joints were welded using a tool tilt angle of 2°,which had the maximum lap shear strength of 14.42 kN and microhardness of HV 132.The joints welded using tool tilt angles of 1°and 3°yielded inferior lap shear strength due to unbalanced material flow in the weld region during FSW.
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.
