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
Friction stir welding （FSW） of 6061 aluminium alloy butt joint was carried out at each rotation speed of 600, 800, 1000, 1200 r/min for two different travel speeds, 80 and 100 mm/min, at a constant probe depth of 1....Friction stir welding （FSW） of 6061 aluminium alloy butt joint was carried out at each rotation speed of 600, 800, 1000, 1200 r/min for two different travel speeds, 80 and 100 mm/min, at a constant probe depth of 1.85 mm. The calculated energy input based on the FSW parameters studied shows that the ultimate tensile strength （UTS） of the butt joint is obtained within a certain range of energy input of 297 kJ to 354 kJ out of total range of energy input studied from 196 kJ to 405 kJ. The fatigue behaviors of high-strength and low-strength joints performed at different stress ratios, i.e., 0.5, 0.3, 0.1, -0.3, -0.5, indicate that the fatigue behaviors of both the welds are sensitive to the microstructural features, such as stir zone （SZ）, thermo mechanically affected zone （TMAZ） and heat affected zone （HAZ）. The observed fatigue strengths were discussed in terms of the microstructure, crack path behavior and fracture surface.展开更多
To expand the application of wire-arc additive manufacturing(WAAM)in aluminum alloy forming com-ponents,it is vitally important to reduce the porosity,refine microstructure,and thereby improve the mechanical propertie...To expand the application of wire-arc additive manufacturing(WAAM)in aluminum alloy forming com-ponents,it is vitally important to reduce the porosity,refine microstructure,and thereby improve the mechanical properties of the components.In this study,the interlayer friction stir processing(FSP)tech-nique was employed to assist the WAAM of 4043 Al-Si alloy,and the related effects on the microstruc-ture evolutions and mechanical properties of the fabricated builds were systematacially investigated.As compared to the conventional WAAM processing of Al-Si alloy,it was found that the introduction of in-terlayer FSP can effectively eliminate the pores,and both theα-Al dendrites and Si-rich eutectic network were severely broken up,leading to a remarkable enhancement in ductility and fatigue performance.The average yield strength(YS)and ultimate tensile strength(UTS)of the Al-based components produced by the combination of WAAM and interlayer FSP methods were 88 and 148 MPa,respectively.Meanwhile,the elongation(EL)of 37.5%and 28.8%can be achieved in the horizontal and vertical directions,respec-tively.Such anisotropy of EL was attributed to the inhomogeneous microstructure in the stir zone(SZ).Notably,the stress concentration can be effectively reduced by the elimination of porosity and Si-rich eu-tectic network fragmentation by the interlayer FSP,and thus the fatigue behavior was improved with the fatigue strength and elongation increased by∼28%and∼108.7%,respectively.It is anticipated that this study will provide a powerful strategy and theoretical guidance for the WAAM fabrication of Al-based alloy components with high ductility and fatigue performance.展开更多
In this investigation, 2024 aluminium alloy plates were friction stir welded, a sequence of experiments was performedincluding fatigue and crack propagation tests in air, under pre-corrosion and in a 3.5% NaCl solutio...In this investigation, 2024 aluminium alloy plates were friction stir welded, a sequence of experiments was performedincluding fatigue and crack propagation tests in air, under pre-corrosion and in a 3.5% NaCl solution, in combination withfractography analyses of near-threshold region, Paris region and finial fracture region with the aid of scanning electron microscopy（SEM）. Results showed that the corrosive environment caused a dramatical decrease in fatigue lives of FS welds, the corrosionfatigue lives of FS welds were almost a half of those of the as-welded specimens. The crack growth rates in FS welds were higherthan their counterparts in base materials, under the corrosive environment, the crack growth rate differences between base materialsand FS welds become increasingly apparent with the increase of stress intensity factor range ΔK, but the pre-corrosion process hadlittle effect on the FS welds’ crack propagation behavior except for shortening the crack initiation lives greatly.展开更多
The aim of the present work is to evaluate the fatigue crack growth behaviour of 12 mm thick AA 7075-T651 aluminium alloy plates joined by FSW. Fatigue crack growth test was carried out on center cracked tensile (CCT)...The aim of the present work is to evaluate the fatigue crack growth behaviour of 12 mm thick AA 7075-T651 aluminium alloy plates joined by FSW. Fatigue crack growth test was carried out on center cracked tensile (CCT) specimens extracted from the FSW joints and unwelded parent metal. Transverse tensile properties of the unwelded parent metal and welded joints were evaluated. Microstructures of the welded joints were analyzed using optical microscopy and transmission electron microscopy. The scanning electron microscope was used to characterize the fracture surfaces. It was found that the ΔKcr of the welded joint is reduced by 10×10-3 MPa·m1/2 in comparison with the unwelded parent metal. Hence, the fatigue life of the friction stir welded AA 7075-T651aluminium alloy joints is appreciably lower than that of the unwelded parent metal, which is attributed to the dissolution of precipitates in the weld region during friction stir welding.展开更多
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.
文摘Friction stir welding （FSW） of 6061 aluminium alloy butt joint was carried out at each rotation speed of 600, 800, 1000, 1200 r/min for two different travel speeds, 80 and 100 mm/min, at a constant probe depth of 1.85 mm. The calculated energy input based on the FSW parameters studied shows that the ultimate tensile strength （UTS） of the butt joint is obtained within a certain range of energy input of 297 kJ to 354 kJ out of total range of energy input studied from 196 kJ to 405 kJ. The fatigue behaviors of high-strength and low-strength joints performed at different stress ratios, i.e., 0.5, 0.3, 0.1, -0.3, -0.5, indicate that the fatigue behaviors of both the welds are sensitive to the microstructural features, such as stir zone （SZ）, thermo mechanically affected zone （TMAZ） and heat affected zone （HAZ）. The observed fatigue strengths were discussed in terms of the microstructure, crack path behavior and fracture surface.
文摘To expand the application of wire-arc additive manufacturing(WAAM)in aluminum alloy forming com-ponents,it is vitally important to reduce the porosity,refine microstructure,and thereby improve the mechanical properties of the components.In this study,the interlayer friction stir processing(FSP)tech-nique was employed to assist the WAAM of 4043 Al-Si alloy,and the related effects on the microstruc-ture evolutions and mechanical properties of the fabricated builds were systematacially investigated.As compared to the conventional WAAM processing of Al-Si alloy,it was found that the introduction of in-terlayer FSP can effectively eliminate the pores,and both theα-Al dendrites and Si-rich eutectic network were severely broken up,leading to a remarkable enhancement in ductility and fatigue performance.The average yield strength(YS)and ultimate tensile strength(UTS)of the Al-based components produced by the combination of WAAM and interlayer FSP methods were 88 and 148 MPa,respectively.Meanwhile,the elongation(EL)of 37.5%and 28.8%can be achieved in the horizontal and vertical directions,respec-tively.Such anisotropy of EL was attributed to the inhomogeneous microstructure in the stir zone(SZ).Notably,the stress concentration can be effectively reduced by the elimination of porosity and Si-rich eu-tectic network fragmentation by the interlayer FSP,and thus the fatigue behavior was improved with the fatigue strength and elongation increased by∼28%and∼108.7%,respectively.It is anticipated that this study will provide a powerful strategy and theoretical guidance for the WAAM fabrication of Al-based alloy components with high ductility and fatigue performance.
基金Project(51405309)supported by the National Natural Science Foundation of ChinaProject(L2014065)supported by the General Project of Scientific Research of Liaoning Provincial Education Department,ChinaProject(2013024011)supported by the Natural Science Foundation of Liaoning Province,China
文摘In this investigation, 2024 aluminium alloy plates were friction stir welded, a sequence of experiments was performedincluding fatigue and crack propagation tests in air, under pre-corrosion and in a 3.5% NaCl solution, in combination withfractography analyses of near-threshold region, Paris region and finial fracture region with the aid of scanning electron microscopy（SEM）. Results showed that the corrosive environment caused a dramatical decrease in fatigue lives of FS welds, the corrosionfatigue lives of FS welds were almost a half of those of the as-welded specimens. The crack growth rates in FS welds were higherthan their counterparts in base materials, under the corrosive environment, the crack growth rate differences between base materialsand FS welds become increasingly apparent with the increase of stress intensity factor range ΔK, but the pre-corrosion process hadlittle effect on the FS welds’ crack propagation behavior except for shortening the crack initiation lives greatly.
文摘The aim of the present work is to evaluate the fatigue crack growth behaviour of 12 mm thick AA 7075-T651 aluminium alloy plates joined by FSW. Fatigue crack growth test was carried out on center cracked tensile (CCT) specimens extracted from the FSW joints and unwelded parent metal. Transverse tensile properties of the unwelded parent metal and welded joints were evaluated. Microstructures of the welded joints were analyzed using optical microscopy and transmission electron microscopy. The scanning electron microscope was used to characterize the fracture surfaces. It was found that the ΔKcr of the welded joint is reduced by 10×10-3 MPa·m1/2 in comparison with the unwelded parent metal. Hence, the fatigue life of the friction stir welded AA 7075-T651aluminium alloy joints is appreciably lower than that of the unwelded parent metal, which is attributed to the dissolution of precipitates in the weld region during friction stir welding.
