The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demo...The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demonstrate that the grains are further squashed and elongated compared with artificial aging due to the existence of the applied stress during the age forming. Meanwhile, the precipitated phases change from circle shape with random orientation of age forming to long strip shape with uniform orientation of artificial aging. The dislocation configuration in samples changes from ring dislocation or helical dislocation of the artificial aging to long and straight dislocation of the age forming. Otherwise, age forming slightly reduces the tensile properties and fracture toughness of the alloy and enhances its fatigue crack growth rate.展开更多
The stress corrosion cracking(SCC)behaviors of 2A12 aluminum alloy after annealing treatment were studied by slow strain rate testing(SSRT),electrochemical polarization measurement,scanning electron microscope(SEM),en...The stress corrosion cracking(SCC)behaviors of 2A12 aluminum alloy after annealing treatment were studied by slow strain rate testing(SSRT),electrochemical polarization measurement,scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and transmission electron microscopy(TEM).Various concentrations of NaCl,H_(2)SO_(4)and HCl aqueous solution were prepared to act as the corrosive solution.The experimental results show that regarding the SCC,2A12 alloy performs best in NaCl solution but worst in HCl solution and intermediately between the above mentioned two cases in H_(2)SO_(4)solution.For the SSRT carried out in room temperature,there is a higher decrease in elongation without large strength loss for the alloy immersed in NaCl solution.With the test conducted in H_(2)SO_(4)solution,there is a higher strength loss and a relatively less loss of elongation compared to the one immersed in NaCl solution.With the test conducted in HCl solution,there is a relativel level loss of strength and elongation compared to either result carried out in NaCl solution or H_(2)SO_(4)solution.展开更多
The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron m...The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The results show that the alloy exhibits higher fatigue crack propagation(FCP) resistance in T3 condition than in T6 condition,the fatigue life is increased by 54% and the fatigue crack growth rate(FCGR) decreases significantly.The fatigue fractures of the alloy in T3 and T6 conditions are transgranular.But in T3 condition,secondary cracks occur and fatigue striations are not clear.In T6 condition,ductile fatigue striations are observed.The effect of aging conditions on fatigue behaviors is explained in terms of the slip planarity of dislocations and the cyclic slip reversibility.展开更多
Ultrasonic assisted friction stir welding (UAFSW) is a recent modification of conventional friction stir welding, which adds ultrasonic energy directly into the friction stir welding area by the pin. In this study, ...Ultrasonic assisted friction stir welding (UAFSW) is a recent modification of conventional friction stir welding, which adds ultrasonic energy directly into the friction stir welding area by the pin. In this study, 2A12 aluminum alloy was welded by this process and conventional, respectively. The tensile tests, microstructure and fracture surface of FSW joint and UAFSW joint were analyzed. The research results show that the surface forming texture of ultrasonic assisted friction stir welding joint, compared with conventional, is finer and more uniform, showing metallic matte color. The grains are much finer in weld nugget zone, thermo-mechanically affected zone and heat-affected zone; S-phase particles size is much smaller and distribution is more homogeneous in the matrix. The tensile strength of UAFSW joint is 94. 13% of base metal, and the elongation is 11.77%. The tensile strength of FSW joint is 83.15% of base metal, and the elongation is 8.81%. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints.展开更多
As a new solid state welding,pinless friction stir welding(PFSW) can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in or...As a new solid state welding,pinless friction stir welding(PFSW) can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 alloy.The results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond defect.For the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone(NZ),deteriorating mechanical properties.Compared with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum alloys.Meanwhile,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.展开更多
The effects of solution temperature and holding time on the microstructure, mechanical properties and surface morphology of 2 A12 aluminum alloy sheets were discussed in this paper. The universal tensile tester was us...The effects of solution temperature and holding time on the microstructure, mechanical properties and surface morphology of 2 A12 aluminum alloy sheets were discussed in this paper. The universal tensile tester was used to test the tensile strength and yield strength of aluminum alloy sheets with different treatment systems. The surface morphology of the alloy sheets was characterized by a white light interference profile scanner, and the microstructure of the sheets was characterized by optical microscope(OM), scanning electron microscope(SEM)and electron backscattered diffraction(EBSD). The results showed that the mechanical properties of the sheets could not satisfy GBT228.1-2010 national standard when the holding time was 10 min and the holding temperature was475 ℃. However, under the other heat treatment systems,the alloy could reach the GBT228.1-2010 national standard. Moreover, with the extension of the holding time, the part of the matrix gradually diffused into the aluminumclad layer. When the holding time was shorter than 25 min,the boundary between the matrix and the aluminum-clad layer was relatively obvious. And the diffusion gradually became obvious when the holding time was over 25 min.Thereby, the boundary became blurry. The further investigation suggested that the solution temperature of495 ℃ and the holding time of 35 min showed better mechanical properties and better surface morphology.展开更多
基金Project (NCET-10-0278) supported by the Program for New Century Excellent Talents in University, ChinaProject (20102024) supported by the Natural Science Foundation of Liaoning Province, China
文摘The comparative experiments of age forming and artificial aging of 2A12 aluminum alloy were carried out. The effect of the age forming on the microstructure and mechanical properties was investigated. The results demonstrate that the grains are further squashed and elongated compared with artificial aging due to the existence of the applied stress during the age forming. Meanwhile, the precipitated phases change from circle shape with random orientation of age forming to long strip shape with uniform orientation of artificial aging. The dislocation configuration in samples changes from ring dislocation or helical dislocation of the artificial aging to long and straight dislocation of the age forming. Otherwise, age forming slightly reduces the tensile properties and fracture toughness of the alloy and enhances its fatigue crack growth rate.
基金Funded by the National Project of Manufacturing and Application Technology of High-performance and Large-size Extruding of Aluminum Alloy(No.2016YFB0300901)。
文摘The stress corrosion cracking(SCC)behaviors of 2A12 aluminum alloy after annealing treatment were studied by slow strain rate testing(SSRT),electrochemical polarization measurement,scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and transmission electron microscopy(TEM).Various concentrations of NaCl,H_(2)SO_(4)and HCl aqueous solution were prepared to act as the corrosive solution.The experimental results show that regarding the SCC,2A12 alloy performs best in NaCl solution but worst in HCl solution and intermediately between the above mentioned two cases in H_(2)SO_(4)solution.For the SSRT carried out in room temperature,there is a higher decrease in elongation without large strength loss for the alloy immersed in NaCl solution.With the test conducted in H_(2)SO_(4)solution,there is a higher strength loss and a relatively less loss of elongation compared to the one immersed in NaCl solution.With the test conducted in HCl solution,there is a relativel level loss of strength and elongation compared to either result carried out in NaCl solution or H_(2)SO_(4)solution.
基金Project(2005CB623705) supported by the National Basic Research Program of China
文摘The fatigue behaviors of 2E12 aluminum alloy in T3 and T6 conditions at room temperature in air were investigated.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The results show that the alloy exhibits higher fatigue crack propagation(FCP) resistance in T3 condition than in T6 condition,the fatigue life is increased by 54% and the fatigue crack growth rate(FCGR) decreases significantly.The fatigue fractures of the alloy in T3 and T6 conditions are transgranular.But in T3 condition,secondary cracks occur and fatigue striations are not clear.In T6 condition,ductile fatigue striations are observed.The effect of aging conditions on fatigue behaviors is explained in terms of the slip planarity of dislocations and the cyclic slip reversibility.
文摘Ultrasonic assisted friction stir welding (UAFSW) is a recent modification of conventional friction stir welding, which adds ultrasonic energy directly into the friction stir welding area by the pin. In this study, 2A12 aluminum alloy was welded by this process and conventional, respectively. The tensile tests, microstructure and fracture surface of FSW joint and UAFSW joint were analyzed. The research results show that the surface forming texture of ultrasonic assisted friction stir welding joint, compared with conventional, is finer and more uniform, showing metallic matte color. The grains are much finer in weld nugget zone, thermo-mechanically affected zone and heat-affected zone; S-phase particles size is much smaller and distribution is more homogeneous in the matrix. The tensile strength of UAFSW joint is 94. 13% of base metal, and the elongation is 11.77%. The tensile strength of FSW joint is 83.15% of base metal, and the elongation is 8.81%. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints.
基金supported by the National Natural Science Foundation of China(No.51204111)the Natural Science Foundation of Liaoning Province(No.2014024008)the Aeronautical Science Foundation of China(No.2014ZE54021)
文摘As a new solid state welding,pinless friction stir welding(PFSW) can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 alloy.The results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond defect.For the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone(NZ),deteriorating mechanical properties.Compared with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum alloys.Meanwhile,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.
基金financially supported by the National Key R&D Program of China (No.2016YFB0300800)。
文摘The effects of solution temperature and holding time on the microstructure, mechanical properties and surface morphology of 2 A12 aluminum alloy sheets were discussed in this paper. The universal tensile tester was used to test the tensile strength and yield strength of aluminum alloy sheets with different treatment systems. The surface morphology of the alloy sheets was characterized by a white light interference profile scanner, and the microstructure of the sheets was characterized by optical microscope(OM), scanning electron microscope(SEM)and electron backscattered diffraction(EBSD). The results showed that the mechanical properties of the sheets could not satisfy GBT228.1-2010 national standard when the holding time was 10 min and the holding temperature was475 ℃. However, under the other heat treatment systems,the alloy could reach the GBT228.1-2010 national standard. Moreover, with the extension of the holding time, the part of the matrix gradually diffused into the aluminumclad layer. When the holding time was shorter than 25 min,the boundary between the matrix and the aluminum-clad layer was relatively obvious. And the diffusion gradually became obvious when the holding time was over 25 min.Thereby, the boundary became blurry. The further investigation suggested that the solution temperature of495 ℃ and the holding time of 35 min showed better mechanical properties and better surface morphology.