A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220°C for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and th...A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220°C for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180°C possess three interfacial layers and mainly consist ofα2-Ti3Al,τ3-Al3NiTi2 and Ti2Ni,but the brazing seams are no longer layered and Ti2Ni is completely replaced by the uniformly distributedτ3-Al3NiTi2 at 1200 and 1220°C due to the destruction ofα2-Ti3Al barrier layer.This transformation at 1200°C obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.展开更多
Tungsten inert gas (TIG) welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG...Tungsten inert gas (TIG) welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG joints represents an important issue in their manufacturing and strength evaluation. Experimental and numerical simulation methods were used to investigate the effects of weld toe shape and weld toe position on the tensile behavior and mechanical properties of these joints. The simulation results indicated that the relative difference in elongation could be as large as 96.9% caused by the difference in weld toe shape. The joints with weld toes located in the weld metal or in the partially melted zone (PMZ) exhibited larger elongation than joints with weld toes located at the juncture of the weld metal and the PMZ.展开更多
The quasi-static and dynamic tensile behaviors in electron beam welded(EBW) Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system(MTS) and reconstructive Hopki...The quasi-static and dynamic tensile behaviors in electron beam welded(EBW) Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system(MTS) and reconstructive Hopkinson bars apparatus.The microstructures of the base metal(BM) and the welded metal(WM) were observed with optical microscope.The fracture characteristics of the BM and WM were characterized with scanning electronic microscope.In Ti-6Al-4V alloy joint,the flow stress of WM is higher than that of BM,while the fracture strain of WM is less than that of BM at strain rates of 103 and 10-3 s-1,respectively.The fracture strain of WM has apparent improvement when the strain rate rises from 10-3 to 103 s-1,while the fracture strain of BM almost has no change.At the same time,the fracture mode of WM alters from brittle to ductile fracture,which causes improvement of the fracture strain of WM.展开更多
The tungsten inert gas welding(TIG) technique was employed to weld the nickel-based wrought superalloy GH625, and the microstructures, element distribution, grain boundary character and mechanical properties of the ...The tungsten inert gas welding(TIG) technique was employed to weld the nickel-based wrought superalloy GH625, and the microstructures, element distribution, grain boundary character and mechanical properties of the welded joint were investigated systematically. The results indicated that the welded seam was of austenite dendrite crystal structure and no obvious heat affected zone(HAZ) was observed. A number of precipitated δ phases with homogeneous distribution were observed in the interdendritic region of the weld fusion zone. The abnormal phenomenon observed in the weld fusion zone of GH625, i.e., higher hardness and larger grain size compared with the base metal, may be attributed to the precipitated δ phase in the weld fusion zone. The higher tensile strength in the base metal was mainly attributed to the presence of more contents of fine grains and twin boundaries, while the lower elongation in the welded joint was mainly owing to the precipitated δ phase.展开更多
The welding property of TiB2/ZL101 composite was investigated using electron beam(EB) welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing para...The welding property of TiB2/ZL101 composite was investigated using electron beam(EB) welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing parameters and scanning rate.The reinforcement particles TiB2 distributed homogeneously in welding seam without any segregation.The tensile results show that fracture occurs at the base metal and elastic modulus increases compared with base metal.Wear resistance of welding seam is improved greatly compared with base metal.The results show that the TiB2/ZL101 composite can be successfully welded by EB technology.展开更多
The influences of axial force on tensile properties of friction stir welded AZ61A magnesium alloy were studied. Five different values of axial forces ranging from 3 to 7 kN were used to fabricate the joints. Tensile p...The influences of axial force on tensile properties of friction stir welded AZ61A magnesium alloy were studied. Five different values of axial forces ranging from 3 to 7 kN were used to fabricate the joints. Tensile properties of the joints were evaluated and correlated with the stir zone microstructure and hardness. From this investigation, it is found that the joint fabricated with an axial force of 5 kN exhibits superior tensile properties compared to other joints. The formation of finer grains in the stir zone and higher hardness of the stir zone are the main reasons for the superior tensile properties of these joints.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
Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardnes...Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.展开更多
AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW) and friction stir welding (FSW) processes. The effects o...AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW) and friction stir welding (FSW) processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.展开更多
Numerical simulation and experimental methods were used to investigate the effects of weld penetration on tensile properties of 2219 aluminum alloy tungsten inert gas(TIG)welded joints.The results show that when other...Numerical simulation and experimental methods were used to investigate the effects of weld penetration on tensile properties of 2219 aluminum alloy tungsten inert gas(TIG)welded joints.The results show that when other geometric parameters are consistent,within a certain range,the deeper the weld penetration of the capping weld is,the lower the tensile strength of the j oint is.The deeper weld penetration of the capping weld can cause the more concentrated stress at the weld toe and the joint is more likely to crack accordingly.Based on necessary assumptions,a model for analyzing the mathematical relation between the weld penetration of the capping weld and the tensile strength of the joint was proposed to validate the experimental results. The decrease of weld penetration of capping weld can be controlled by decreasing welding current,helium content or increasing welding voltage.展开更多
基金the National Natural Science Foundation of China(No.51865012)the Natural Science Foundation of Jiangxi Province,China(No.20202BABL204040)+3 种基金the Open Foundation of National Engineering Research Center of Near-net-shape Forming for Metallic Materials,China(No.2016005)the Science Foundation of Educational Department of Jiangxi Province,China(No.GJJ170372)the GF Basic Scientific Research Project,China(No.JCKY2020205C002)the Civil Population Supporting Planning and Development Project,China(No.JPPT125GH038).
文摘A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220°C for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180°C possess three interfacial layers and mainly consist ofα2-Ti3Al,τ3-Al3NiTi2 and Ti2Ni,but the brazing seams are no longer layered and Ti2Ni is completely replaced by the uniformly distributedτ3-Al3NiTi2 at 1200 and 1220°C due to the destruction ofα2-Ti3Al barrier layer.This transformation at 1200°C obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.
文摘Tungsten inert gas (TIG) welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG joints represents an important issue in their manufacturing and strength evaluation. Experimental and numerical simulation methods were used to investigate the effects of weld toe shape and weld toe position on the tensile behavior and mechanical properties of these joints. The simulation results indicated that the relative difference in elongation could be as large as 96.9% caused by the difference in weld toe shape. The joints with weld toes located in the weld metal or in the partially melted zone (PMZ) exhibited larger elongation than joints with weld toes located at the juncture of the weld metal and the PMZ.
文摘The quasi-static and dynamic tensile behaviors in electron beam welded(EBW) Ti-6Al-4V alloy were investigated at strain rates of 10-3 and 103 s-1,respectively,by materials test system(MTS) and reconstructive Hopkinson bars apparatus.The microstructures of the base metal(BM) and the welded metal(WM) were observed with optical microscope.The fracture characteristics of the BM and WM were characterized with scanning electronic microscope.In Ti-6Al-4V alloy joint,the flow stress of WM is higher than that of BM,while the fracture strain of WM is less than that of BM at strain rates of 103 and 10-3 s-1,respectively.The fracture strain of WM has apparent improvement when the strain rate rises from 10-3 to 103 s-1,while the fracture strain of BM almost has no change.At the same time,the fracture mode of WM alters from brittle to ductile fracture,which causes improvement of the fracture strain of WM.
文摘The tungsten inert gas welding(TIG) technique was employed to weld the nickel-based wrought superalloy GH625, and the microstructures, element distribution, grain boundary character and mechanical properties of the welded joint were investigated systematically. The results indicated that the welded seam was of austenite dendrite crystal structure and no obvious heat affected zone(HAZ) was observed. A number of precipitated δ phases with homogeneous distribution were observed in the interdendritic region of the weld fusion zone. The abnormal phenomenon observed in the weld fusion zone of GH625, i.e., higher hardness and larger grain size compared with the base metal, may be attributed to the precipitated δ phase in the weld fusion zone. The higher tensile strength in the base metal was mainly attributed to the presence of more contents of fine grains and twin boundaries, while the lower elongation in the welded joint was mainly owing to the precipitated δ phase.
基金Project(11ZR1417500) supported by Natural Science Foundation of Shanghai,China
文摘The welding property of TiB2/ZL101 composite was investigated using electron beam(EB) welding experimental system with a function generator.The fine defect-free welding seam was obtained under proper processing parameters and scanning rate.The reinforcement particles TiB2 distributed homogeneously in welding seam without any segregation.The tensile results show that fracture occurs at the base metal and elastic modulus increases compared with base metal.Wear resistance of welding seam is improved greatly compared with base metal.The results show that the TiB2/ZL101 composite can be successfully welded by EB technology.
基金University Grants Commission (UGC),New Delhi for their financial support rendered through Junior Research Fellowship (JRF) award
文摘The influences of axial force on tensile properties of friction stir welded AZ61A magnesium alloy were studied. Five different values of axial forces ranging from 3 to 7 kN were used to fabricate the joints. Tensile properties of the joints were evaluated and correlated with the stir zone microstructure and hardness. From this investigation, it is found that the joint fabricated with an axial force of 5 kN exhibits superior tensile properties compared to other joints. The formation of finer grains in the stir zone and higher hardness of the stir zone are the main reasons for the superior tensile properties of these joints.
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Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.
基金Project DRAO/08/1061356/M1 supported by Aeronautical Research & Development Board (ARDB),New Delhi,India
文摘AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding (GTAW), electron beam welding (EBW) and friction stir welding (FSW) processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.
基金Project(U1637601)supported by the Joint Funds of the National Natural Science Foundation of China
文摘Numerical simulation and experimental methods were used to investigate the effects of weld penetration on tensile properties of 2219 aluminum alloy tungsten inert gas(TIG)welded joints.The results show that when other geometric parameters are consistent,within a certain range,the deeper the weld penetration of the capping weld is,the lower the tensile strength of the j oint is.The deeper weld penetration of the capping weld can cause the more concentrated stress at the weld toe and the joint is more likely to crack accordingly.Based on necessary assumptions,a model for analyzing the mathematical relation between the weld penetration of the capping weld and the tensile strength of the joint was proposed to validate the experimental results. The decrease of weld penetration of capping weld can be controlled by decreasing welding current,helium content or increasing welding voltage.