The ultrasonic assisted tungsten inert gas （U-TIG） welding is a newly developed arc welding method, which is aimed at improving the weld quality and efficiency. TIG welding and U-TIG welding of 2014 aluminum alloy w...The ultrasonic assisted tungsten inert gas （U-TIG） welding is a newly developed arc welding method, which is aimed at improving the weld quality and efficiency. TIG welding and U-TIG welding of 2014 aluminum alloy with 5 mm thickness were experimentally carried out in this paper. The microstructure and porosity of welded joints were analyzed. Compared with conventional TIG welding, the columnar crystals are changed into equiaxed crystals at the centre of weld zone and the grain of fusion zone in U-TIG welding is refined and equiaxed. The porosities of joint decrease after the ultrasonic was applied on the arc. The mechanism of crystal grain refinement is discussed in this paper and the reasons of porosity decrease in U-TIG welded joint may be due to the effect of acoustic streaming and cavitation, which need further research.展开更多
AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas （VPTIG） welding process and the effects of post weld heat treatment （PWHT） on the tensile properties, microstructure and fatigu...AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas （VPTIG） welding process and the effects of post weld heat treatment （PWHT） on the tensile properties, microstructure and fatigue behaviour of the welded joints were investigated. The VPTIG welding process was adopted because it could meet the need of cathode cleaning and meanwhile it could reduce the deterioration of tungsten electrode furthest. The welded samples were divided into as-welded （AW） sample and PWHT sample. The PWHT method used on the samples was solution treatment （535 ℃, 30 rain）, water quenching and artificial aging （175 ℃, 12 h）. The experimental results show that, compared with the AW samples, the microstructure characteristics and mechanical properties of the AA2219 joints after PWHT were significantly improved. The improvement of yield strength, ultimate tensile strength, and fatigue strength are 42.6%, 43.1% and 18.4%, respectively.展开更多
Tungsten inert gas （TIG） welding-brazing technology using Mg-based filler was developed to join AZ31 B Mg alloy to TC4 Ti alloy in a lap configuration. The results indicate that robust joints can be obtained with we...Tungsten inert gas （TIG） welding-brazing technology using Mg-based filler was developed to join AZ31 B Mg alloy to TC4 Ti alloy in a lap configuration. The results indicate that robust joints can be obtained with welding current in the range of 60-70 A. The joint interface was found to be likely composed of Mg-Ti diffusion reaction layer accompanied with Mg17Al12 precipitate phase, indicating that metallurgical joining was achieved. The optimized joint with average tensile-shear strength of 190 N/mm^2 was obtained and fracture occurred at the Ti/fusion zone interracial layer during tensile test. Moreover. the fracture surface was characterized by equiaxed dimple patterns accompanied with a few lamellar tearing. Finally, finite element modeling （FEM） numerical simulation was developed to analyze the distribution characteristics of the temperature field of joints.展开更多
文摘The ultrasonic assisted tungsten inert gas （U-TIG） welding is a newly developed arc welding method, which is aimed at improving the weld quality and efficiency. TIG welding and U-TIG welding of 2014 aluminum alloy with 5 mm thickness were experimentally carried out in this paper. The microstructure and porosity of welded joints were analyzed. Compared with conventional TIG welding, the columnar crystals are changed into equiaxed crystals at the centre of weld zone and the grain of fusion zone in U-TIG welding is refined and equiaxed. The porosities of joint decrease after the ultrasonic was applied on the arc. The mechanism of crystal grain refinement is discussed in this paper and the reasons of porosity decrease in U-TIG welded joint may be due to the effect of acoustic streaming and cavitation, which need further research.
基金Project(51275343)supported by the National Natural Science Foundation of China
文摘AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas （VPTIG） welding process and the effects of post weld heat treatment （PWHT） on the tensile properties, microstructure and fatigue behaviour of the welded joints were investigated. The VPTIG welding process was adopted because it could meet the need of cathode cleaning and meanwhile it could reduce the deterioration of tungsten electrode furthest. The welded samples were divided into as-welded （AW） sample and PWHT sample. The PWHT method used on the samples was solution treatment （535 ℃, 30 rain）, water quenching and artificial aging （175 ℃, 12 h）. The experimental results show that, compared with the AW samples, the microstructure characteristics and mechanical properties of the AA2219 joints after PWHT were significantly improved. The improvement of yield strength, ultimate tensile strength, and fatigue strength are 42.6%, 43.1% and 18.4%, respectively.
基金financial support by the National Natural Science Foundation of China (No. 51205428)the Fundamental Research Funds for the Central Universities (Nos. CDJZR13130040 and CDJZR12130047)
文摘Tungsten inert gas （TIG） welding-brazing technology using Mg-based filler was developed to join AZ31 B Mg alloy to TC4 Ti alloy in a lap configuration. The results indicate that robust joints can be obtained with welding current in the range of 60-70 A. The joint interface was found to be likely composed of Mg-Ti diffusion reaction layer accompanied with Mg17Al12 precipitate phase, indicating that metallurgical joining was achieved. The optimized joint with average tensile-shear strength of 190 N/mm^2 was obtained and fracture occurred at the Ti/fusion zone interracial layer during tensile test. Moreover. the fracture surface was characterized by equiaxed dimple patterns accompanied with a few lamellar tearing. Finally, finite element modeling （FEM） numerical simulation was developed to analyze the distribution characteristics of the temperature field of joints.
