The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and analyzed.Results show that the static compression load of t...The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and analyzed.Results show that the static compression load of the typical structure connected by riveting and refill FSSW fluctuated in the range of 117-124 kN,and the shear load was in the range of 89-95 kN.Welds spacing had a small influence on the static load of the structures joined by refill FSSW.However,the fatigue life of riveted structures was lower than that joined by refill FSSW.For the welded structure,the heterogeneous microstructures of the welded joint led to the uneven microhardness,and the hook at the lap interface bent upwards at the same time.These factors made the welded structures during the fatigue test failure along the path of sleeve moving.展开更多
In this paper,6 mm thick 2219-T6 aluminum alloy was joined by means of variable polarity tungsten-arc welding( VP-TIG) and the influence of gradient mismatches on VP-TIG joints is investigated. The average tensile str...In this paper,6 mm thick 2219-T6 aluminum alloy was joined by means of variable polarity tungsten-arc welding( VP-TIG) and the influence of gradient mismatches on VP-TIG joints is investigated. The average tensile strength of the joints reduces 32%,53% and 59%,when the mismatch of the joint was 0. 635 mm,1. 44 mm,1. 83 mm,respectively.Incomplete penetration,additional bending moment( Ma) and decrease of effective load region area are considered to explain this phenomenon. The fracture location of tensile specimens occurred at the weld zone( WZ) close to partial melt zone( PMZ),corresponding to a sharp decline of microhardness from PMZ to WZ. The original position of fracture is found at weld toe,where incomplete penetration forms due to the introduction of gradient mismatches.展开更多
Repair welding of AA 6082-T6 joints was carried out using ER 4043 filler through the TIG welding process with or without pulsed current.Microstructure and mechanical characteristics of the joints before and after repa...Repair welding of AA 6082-T6 joints was carried out using ER 4043 filler through the TIG welding process with or without pulsed current.Microstructure and mechanical characteristics of the joints before and after repairing were investigated by examining macrostructure,microstructure,and distributions of porosity in the weld metal(WM),and by hardness,tensile,and bending tests.We observed that the welding current,phase transformations in heat-affected zone(HAZ)and porosity introduced in the WM during welding influence on its mechanical properties in sequence.The experimental results showed that the bead width and penetration as well as size of pores in the joints were mainly influenced by the welding currents.The sound joints were obtained at a welding current of 140 A with or without pulsed current when welding speed and gas flow rate were set at 20 cm·min-1 and 15 L·min-1,respectively.Among them,the decrease in mechanical properties of repair weld(RW)was directly related to the phase transformations in the over-ageing zone due to the double welding thermal cycles and elevated distribution of porosity in the WM.In addition,it was observed that the comparatively smaller grain size and lower porosity in WM of the RW produced by pulsed TIG welding gave a positive effect on its mechanical properties.展开更多
The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted main...The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg2Si particles. The interface zone had a double-layer structure： Fe2Al5 layer at steel side and Fe4Al13 layer at Al nugget side. The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains. When alloy elements Cu, Zn, Ti and Ni were added, the tensile shear load of Al-steel joints reached 2 780 N, 2 910 N, 2 915 N and 2 929 N respectively, which increased by 24. 1%, 29.9%, 30. 1% and 30. 7% respectively compared with that （2 241 N） of joint without nugget alloying. Therefore, it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.展开更多
In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of tem...In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.展开更多
The influences of multiple plastic deformations on microstructure and mechanical properties of 7A04-T6 alloy by isothermal compression experiments in different passes deformation on the 6300 kN extrusion press. The ex...The influences of multiple plastic deformations on microstructure and mechanical properties of 7A04-T6 alloy by isothermal compression experiments in different passes deformation on the 6300 kN extrusion press. The experimental results showed that the strength and elongation of 7A04-T6 alloy were increased firstly and then decreased as the deformation pass increases at above 400 ℃. The grains of 7A04-T6 alloy was refined firstly and then grow, the grain was become refinement after four deformations under this experimental conditions. The second phase η (MgZn2) in the matrix would precipitate after solution, precipitation strengthening taking place. It is obvious that the number of second phase which dissolve into the matrix will increase as the deformation pass increasing. So the tensile strength reached the highest after four deformations, is 590.9 MPa, yield strength is 532.5 MPa, and elongation is 12.4%. After four deformations of 7A04-T6 alloy, tensile fracture surface of samples was composed of the deep and uniform dimples, belonging to ductile fracture. Therefore, 7A04-T6 alloy has better comprehensive mechanical properties after four deformations.展开更多
The initial corrosion behavior and mechanism of 7B04 aluminum alloy under acid immersion and salt spray environments(pH=3.5)are studied by Scanning Electron Microscope(SEM),optical microscope,Fourier Transform Infrare...The initial corrosion behavior and mechanism of 7B04 aluminum alloy under acid immersion and salt spray environments(pH=3.5)are studied by Scanning Electron Microscope(SEM),optical microscope,Fourier Transform Infrared Spectroscopy(FT-IR),X-Ray Diffraction(XRD),potentiodynamic polarization,Electrochemical Impedance Spectroscopy(EIS),and Scanning Kelvin Probe(SKP).The results show that pitting corrosion occurs at the initial corrosion stage,and the potential difference between the second phase particles is the main cause of pitting.Pitting pits on different locations gradually expand and coalesce with the proceeding of corrosion.The main components of corrosion products are Al_(2)O_(3),Al(OH)_(3),and AlCl_(3),and the generation rate of the corrosion product layer under the salt spray environment is larger than that under acid immersion environment.Under both environments,the Volta potential distribution first disperses and then concentrates,while the charge transfer resistance first decreases and then increases with the corrosion time.The Volta potential gradually shifts in a positive direction,indicating that corrosion products have an inhibitory effect on corrosion.After the same corrosion time,the corrosion product layer resistance and the expectation of the Volta potential of the salt spray sample are higher than those of the immersion sample.Comparatively,the corrosion current density for the salt spray sample is significantly lower than the immersion sample,which indicates that the thicker the corrosion product layer,the stronger the inhibition of corrosion reaction.展开更多
文摘The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and analyzed.Results show that the static compression load of the typical structure connected by riveting and refill FSSW fluctuated in the range of 117-124 kN,and the shear load was in the range of 89-95 kN.Welds spacing had a small influence on the static load of the structures joined by refill FSSW.However,the fatigue life of riveted structures was lower than that joined by refill FSSW.For the welded structure,the heterogeneous microstructures of the welded joint led to the uneven microhardness,and the hook at the lap interface bent upwards at the same time.These factors made the welded structures during the fatigue test failure along the path of sleeve moving.
基金supported by the National Natural Science Foundation of China(No.50904020)the Fundamental Research Funds for the Central Universities(No.HIT.NSRIF.2012007)
文摘In this paper,6 mm thick 2219-T6 aluminum alloy was joined by means of variable polarity tungsten-arc welding( VP-TIG) and the influence of gradient mismatches on VP-TIG joints is investigated. The average tensile strength of the joints reduces 32%,53% and 59%,when the mismatch of the joint was 0. 635 mm,1. 44 mm,1. 83 mm,respectively.Incomplete penetration,additional bending moment( Ma) and decrease of effective load region area are considered to explain this phenomenon. The fracture location of tensile specimens occurred at the weld zone( WZ) close to partial melt zone( PMZ),corresponding to a sharp decline of microhardness from PMZ to WZ. The original position of fracture is found at weld toe,where incomplete penetration forms due to the introduction of gradient mismatches.
基金Funded by the Center of Excellence in Metals and Materials Engineering(CEMME),Faculty of Engineering,Prince of Songkla UniversitySupported by the National Science,Research and Innovation Fund(NSRF)and Prince of Songkla University(No.ENG6505079S)。
文摘Repair welding of AA 6082-T6 joints was carried out using ER 4043 filler through the TIG welding process with or without pulsed current.Microstructure and mechanical characteristics of the joints before and after repairing were investigated by examining macrostructure,microstructure,and distributions of porosity in the weld metal(WM),and by hardness,tensile,and bending tests.We observed that the welding current,phase transformations in heat-affected zone(HAZ)and porosity introduced in the WM during welding influence on its mechanical properties in sequence.The experimental results showed that the bead width and penetration as well as size of pores in the joints were mainly influenced by the welding currents.The sound joints were obtained at a welding current of 140 A with or without pulsed current when welding speed and gas flow rate were set at 20 cm·min-1 and 15 L·min-1,respectively.Among them,the decrease in mechanical properties of repair weld(RW)was directly related to the phase transformations in the over-ageing zone due to the double welding thermal cycles and elevated distribution of porosity in the WM.In addition,it was observed that the comparatively smaller grain size and lower porosity in WM of the RW produced by pulsed TIG welding gave a positive effect on its mechanical properties.
基金supported by National Natural Science Foundation of China(51275204)
文摘The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg2Si particles. The interface zone had a double-layer structure： Fe2Al5 layer at steel side and Fe4Al13 layer at Al nugget side. The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains. When alloy elements Cu, Zn, Ti and Ni were added, the tensile shear load of Al-steel joints reached 2 780 N, 2 910 N, 2 915 N and 2 929 N respectively, which increased by 24. 1%, 29.9%, 30. 1% and 30. 7% respectively compared with that （2 241 N） of joint without nugget alloying. Therefore, it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.
基金the National Natural Science Foundation of China (No.51204111)the Education Department Foundation of Liaoning Province (No.L2012047)the State Key Lab of Advanced Welding and Joining in Harbin Institute of Technology (AWJ-M13-07)
文摘In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.
基金National Defense Foundation Scientific Research (B332006031-1)Youth Foundation of Shanxi Province (2008021030)Natural Science Foundation of Shanxi Province (2009011028-1)
文摘The influences of multiple plastic deformations on microstructure and mechanical properties of 7A04-T6 alloy by isothermal compression experiments in different passes deformation on the 6300 kN extrusion press. The experimental results showed that the strength and elongation of 7A04-T6 alloy were increased firstly and then decreased as the deformation pass increases at above 400 ℃. The grains of 7A04-T6 alloy was refined firstly and then grow, the grain was become refinement after four deformations under this experimental conditions. The second phase η (MgZn2) in the matrix would precipitate after solution, precipitation strengthening taking place. It is obvious that the number of second phase which dissolve into the matrix will increase as the deformation pass increasing. So the tensile strength reached the highest after four deformations, is 590.9 MPa, yield strength is 532.5 MPa, and elongation is 12.4%. After four deformations of 7A04-T6 alloy, tensile fracture surface of samples was composed of the deep and uniform dimples, belonging to ductile fracture. Therefore, 7A04-T6 alloy has better comprehensive mechanical properties after four deformations.
基金co-supported by the China Postdoctoral Science Foundation(No.2019M653929)the Green Innovation Science+1 种基金Technology Plan of CollegesUniversities in Shandong Province,China(No.2020KJA014).
文摘The initial corrosion behavior and mechanism of 7B04 aluminum alloy under acid immersion and salt spray environments(pH=3.5)are studied by Scanning Electron Microscope(SEM),optical microscope,Fourier Transform Infrared Spectroscopy(FT-IR),X-Ray Diffraction(XRD),potentiodynamic polarization,Electrochemical Impedance Spectroscopy(EIS),and Scanning Kelvin Probe(SKP).The results show that pitting corrosion occurs at the initial corrosion stage,and the potential difference between the second phase particles is the main cause of pitting.Pitting pits on different locations gradually expand and coalesce with the proceeding of corrosion.The main components of corrosion products are Al_(2)O_(3),Al(OH)_(3),and AlCl_(3),and the generation rate of the corrosion product layer under the salt spray environment is larger than that under acid immersion environment.Under both environments,the Volta potential distribution first disperses and then concentrates,while the charge transfer resistance first decreases and then increases with the corrosion time.The Volta potential gradually shifts in a positive direction,indicating that corrosion products have an inhibitory effect on corrosion.After the same corrosion time,the corrosion product layer resistance and the expectation of the Volta potential of the salt spray sample are higher than those of the immersion sample.Comparatively,the corrosion current density for the salt spray sample is significantly lower than the immersion sample,which indicates that the thicker the corrosion product layer,the stronger the inhibition of corrosion reaction.
