Hook defect is one of the trickiest issues for friction stir lap welding,which remains to be resolved.In this study,a designed pin with an enlarged-end was proposed to control the interfacial hook defect by optimizing...Hook defect is one of the trickiest issues for friction stir lap welding,which remains to be resolved.In this study,a designed pin with an enlarged-end was proposed to control the interfacial hook defect by optimizing its morphology orientation.The insert aduncous structure at the advancing side is dissected by multilayer metallographic observation,which is the main character to terminate the inner-ward extension of the hook.The application of this tool was verified practical with a varied plunge depth of pin into the lower plate from 0.1 mm to 1.6 mm.The angle of the hook was small and terminated at the insert-structure or oriented toward the material convergence region.No joint fractured along the hook line and the highest joint efficiency reached 86%of the parent 6082-T4 aluminum alloy.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
基金supported by the National Natural Science Foundation of China(No.51575132)。
文摘Hook defect is one of the trickiest issues for friction stir lap welding,which remains to be resolved.In this study,a designed pin with an enlarged-end was proposed to control the interfacial hook defect by optimizing its morphology orientation.The insert aduncous structure at the advancing side is dissected by multilayer metallographic observation,which is the main character to terminate the inner-ward extension of the hook.The application of this tool was verified practical with a varied plunge depth of pin into the lower plate from 0.1 mm to 1.6 mm.The angle of the hook was small and terminated at the insert-structure or oriented toward the material convergence region.No joint fractured along the hook line and the highest joint efficiency reached 86%of the parent 6082-T4 aluminum alloy.
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.
