An attempt is made to measure three direction forces using octagonal ring dynamometer in the 2024 aluminum alloy friction stir joining(FSJ)process.A test is made to measure the specific area stress and stress distribu...An attempt is made to measure three direction forces using octagonal ring dynamometer in the 2024 aluminum alloy friction stir joining(FSJ)process.A test is made to measure the specific area stress and stress distributions in the specific area of the workpiece are obtained.The workpiece stresses in the FSJ process are analyzed by numerical simulation method.It is found that,in the downward stage of the process,feed force and lateral force in the tool are small,almost zero,and the maximum axial force can reach 12.5kN.In the stable joining stage,the forces acting on the tool become stabilized.Compared with the low speed,high feed speed results in small feed force and small lateral force,but large feed force in the stable joining stage.The stresses in three directions of feed direction,direction that perpendicular to butt face and direction perpendicular to the surface are obtained.The simulation stress value of measure point is obtained.Test and numerical simulation can authenticate each other.Both experimental stress values and numerical simulation stress values are credible.展开更多
Two dissimilar magnesium(Mg)alloy sheets,one with low aluminium(AZ31)and another with high aluminium(AZ91)content,were successfully joined by friction stir welding(FSW).The effect of process parameters on the formatio...Two dissimilar magnesium(Mg)alloy sheets,one with low aluminium(AZ31)and another with high aluminium(AZ91)content,were successfully joined by friction stir welding(FSW).The effect of process parameters on the formation of hot cracks was investigated.A sound metallurgical joint was obtained at optimized process parameters(1400 rpm with 25 mm/min feed)which contained fine grains and distributed β(Mg_(17)Al_(12))phase within the nugget zone.An increasing trend in the hardness measurements has also confirmed more amount of dissolution of aluminium within the nugget zone.A sharp interface between nugget zone and thermo mechanical affected zone(TMAZ)was clearly noticed at the AZ31 Mg alloy side(advancing)but not on the AZ91 Mg alloy side(retreating).From the results it can be concluded that FSW can be effectively used to join dissimilar metals,particularly difficult to process metals such as Mg alloys,and hot cracking can be completely eliminated by choosing appropriate process parameters to achieve sound joint.展开更多
Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/...Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.展开更多
Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding （FSW）. A heat input model reported for similar FSW was simplified and used to investigate ...Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding （FSW）. A heat input model reported for similar FSW was simplified and used to investigate the effects of welding speed, rotation speed and tool shoulder diameter on the microstructure and properties of dissimilar welds. The comparison between microstructure, intermetallics and strength of welds shows the good conformity between the results and the calculated heat input factor （HIF） achieved from the model. The joint strength is controlled by Al/Fe interface at HIF of 0.2-0.4, by TMAZ at HIF of 0.4-0.8 and by intermetallics and/or defects at HIF0.8.展开更多
The Hopkinson pressure bar tests for base metal and friction stir jointing ( FSJ ) jointed region of 7022aluminum alloy are carried out at different temperatures and strain rates.The temperature is 30 - 400°C and...The Hopkinson pressure bar tests for base metal and friction stir jointing ( FSJ ) jointed region of 7022aluminum alloy are carried out at different temperatures and strain rates.The temperature is 30 - 400°C and the strain rate is 1 200 - 5 000s -1 .High strain rate for base metal and FSJ jointed region of 7022aluminum alloy are studied.The corresponding stress-strain curves are obtained.The results show that the flow stresses of base metal and FSJ jointed region of 7022aluminum alloy decline with the increase of temperature and increase with the increase of strain rate.Furthermore , the constitutive equation for base metal and FSJ jointed region of 7022aluminum alloy at high temperature and high strain rate is obtained based on Johnson-Cook model.展开更多
The use of light metals today is of great importance,for example in the automotive,aviation and aerospace industries,where energy consumption is minimized and thus the economy is being attempted.By using light metals,...The use of light metals today is of great importance,for example in the automotive,aviation and aerospace industries,where energy consumption is minimized and thus the economy is being attempted.By using light metals,weight is reduced so that energy is saved.Aluminum and magnesium alloys are particularly used thanks to their lightweight.Vehicles in the automotive,aerospace and space industries are expected not only to have lightweight but also high static and dynamic strengths since they are exposed to static and dynamic cyclic loads.However,the structural components can quickly become fatigued and fail under cyclic load due to the notch factor of the joining zones.Compared to the fusion welding method,joining of material is realized mechanically below the melting point of the material in the friction stir spot welding(FSSW)method.Thus,the fatigue strength of the assembly is much higher than that of the fusion welding.In this study,light metal alloy of magnesium AZ31B and aluminum EN AW 2024 were joined with FSSW method and mechanical properties of this joins were also carried out.展开更多
SiCp/Al composites have excellent comprehensive properties and have been widely used in aerospace,automotive industry and other fields.Due to the huge difference in performance between SiC particles and matrix alloys,...SiCp/Al composites have excellent comprehensive properties and have been widely used in aerospace,automotive industry and other fields.Due to the huge difference in performance between SiC particles and matrix alloys,traditional fusion welding methods are difficult to meet the join requirements of SiCp/Al composites.Friction stir joining(friction stir welding),as a solid phase joining process,has been proved to be a new technology with fine prospect in joining SiCp/Al composites compared with fusion welding process.Although some progress has been made in recent years,there are still full of challenges.In this paper,the research status of friction stir joining of SiCp/Al composites in recent years is expatiated,including the weldability of SiCp/Al composites,the macrostructure and the microstructure of joints,mechanical properties of joints,and tool wear and monitoring.Furthermore,the existing challenges of friction stir joining of SiCp/Al composites are summarized and the future development directions are prospected.展开更多
基金supported by the National Natural Science Foundation of China(51175255)the Funding of Jiangsu Innovation Program for Graduate Education(CXZZ13_0152)the Fundamental Research Funds for the Central Universities in P.R.China
文摘An attempt is made to measure three direction forces using octagonal ring dynamometer in the 2024 aluminum alloy friction stir joining(FSJ)process.A test is made to measure the specific area stress and stress distributions in the specific area of the workpiece are obtained.The workpiece stresses in the FSJ process are analyzed by numerical simulation method.It is found that,in the downward stage of the process,feed force and lateral force in the tool are small,almost zero,and the maximum axial force can reach 12.5kN.In the stable joining stage,the forces acting on the tool become stabilized.Compared with the low speed,high feed speed results in small feed force and small lateral force,but large feed force in the stable joining stage.The stresses in three directions of feed direction,direction that perpendicular to butt face and direction perpendicular to the surface are obtained.The simulation stress value of measure point is obtained.Test and numerical simulation can authenticate each other.Both experimental stress values and numerical simulation stress values are credible.
文摘Two dissimilar magnesium(Mg)alloy sheets,one with low aluminium(AZ31)and another with high aluminium(AZ91)content,were successfully joined by friction stir welding(FSW).The effect of process parameters on the formation of hot cracks was investigated.A sound metallurgical joint was obtained at optimized process parameters(1400 rpm with 25 mm/min feed)which contained fine grains and distributed β(Mg_(17)Al_(12))phase within the nugget zone.An increasing trend in the hardness measurements has also confirmed more amount of dissolution of aluminium within the nugget zone.A sharp interface between nugget zone and thermo mechanical affected zone(TMAZ)was clearly noticed at the AZ31 Mg alloy side(advancing)but not on the AZ91 Mg alloy side(retreating).From the results it can be concluded that FSW can be effectively used to join dissimilar metals,particularly difficult to process metals such as Mg alloys,and hot cracking can be completely eliminated by choosing appropriate process parameters to achieve sound joint.
基金This work was supported by International Science and Technology Cooperation Project of Guangdong Province(Grant No.2022A0505050054)Innovation and Technology Fund(ITF)(Grant No.ITP/021/19AP)National Natural Science Foundation of China(Grant No.51905112).
文摘Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.
文摘Defect-free butt joints of 3003 Al alloy to mild steel plates with 3 mm thickness were performed using friction stir welding （FSW）. A heat input model reported for similar FSW was simplified and used to investigate the effects of welding speed, rotation speed and tool shoulder diameter on the microstructure and properties of dissimilar welds. The comparison between microstructure, intermetallics and strength of welds shows the good conformity between the results and the calculated heat input factor （HIF） achieved from the model. The joint strength is controlled by Al/Fe interface at HIF of 0.2-0.4, by TMAZ at HIF of 0.4-0.8 and by intermetallics and/or defects at HIF0.8.
基金Supported by the National Natural Science Foundation of China(51175255)the University Natural Science Foundation of Anhui Province(KJ2012Z388)the Scientific Research Starting Foundation for Talent of Huang-shan University(2012xkjq001)
文摘The Hopkinson pressure bar tests for base metal and friction stir jointing ( FSJ ) jointed region of 7022aluminum alloy are carried out at different temperatures and strain rates.The temperature is 30 - 400°C and the strain rate is 1 200 - 5 000s -1 .High strain rate for base metal and FSJ jointed region of 7022aluminum alloy are studied.The corresponding stress-strain curves are obtained.The results show that the flow stresses of base metal and FSJ jointed region of 7022aluminum alloy decline with the increase of temperature and increase with the increase of strain rate.Furthermore , the constitutive equation for base metal and FSJ jointed region of 7022aluminum alloy at high temperature and high strain rate is obtained based on Johnson-Cook model.
文摘The use of light metals today is of great importance,for example in the automotive,aviation and aerospace industries,where energy consumption is minimized and thus the economy is being attempted.By using light metals,weight is reduced so that energy is saved.Aluminum and magnesium alloys are particularly used thanks to their lightweight.Vehicles in the automotive,aerospace and space industries are expected not only to have lightweight but also high static and dynamic strengths since they are exposed to static and dynamic cyclic loads.However,the structural components can quickly become fatigued and fail under cyclic load due to the notch factor of the joining zones.Compared to the fusion welding method,joining of material is realized mechanically below the melting point of the material in the friction stir spot welding(FSSW)method.Thus,the fatigue strength of the assembly is much higher than that of the fusion welding.In this study,light metal alloy of magnesium AZ31B and aluminum EN AW 2024 were joined with FSSW method and mechanical properties of this joins were also carried out.
基金supported by the National Natural Science Foundation of China(No.51675270)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX17_0241)the China Postdoctoral Science Foundation(No.2016M600411)。
文摘SiCp/Al composites have excellent comprehensive properties and have been widely used in aerospace,automotive industry and other fields.Due to the huge difference in performance between SiC particles and matrix alloys,traditional fusion welding methods are difficult to meet the join requirements of SiCp/Al composites.Friction stir joining(friction stir welding),as a solid phase joining process,has been proved to be a new technology with fine prospect in joining SiCp/Al composites compared with fusion welding process.Although some progress has been made in recent years,there are still full of challenges.In this paper,the research status of friction stir joining of SiCp/Al composites in recent years is expatiated,including the weldability of SiCp/Al composites,the macrostructure and the microstructure of joints,mechanical properties of joints,and tool wear and monitoring.Furthermore,the existing challenges of friction stir joining of SiCp/Al composites are summarized and the future development directions are prospected.
