The electrochemical features of commercial airfrarne material, Al alloy LY12, in 0.349mol/L neutral sodium chloride (NaCl) and sodium sulfate (NazSO^) solutions were investigated by electrochemical impedance spectrosc...The electrochemical features of commercial airfrarne material, Al alloy LY12, in 0.349mol/L neutral sodium chloride (NaCl) and sodium sulfate (NazSO^) solutions were investigated by electrochemical impedance spectroscopy (EIS) and potentiody-namic polarization techniques. The microstructure of the as-tested samples was studied by scanning electron microscopy. The results show that the Nyquist plots of LY12 at different immersion time displayed different features, indicating that the Cl- ions elevate the corrosion rate and inhibit the repassivation of a metastable pit. It also shows that the corrosion product of LY12 formed in SO42- solution isn't easy to dissolve, and it will cover the surface of working electrode in the electrolyte. SEM images indicate that the corrosion apparent area and pit number of LY12 in NaCl solution are greater than that in Na2SO4 solution.展开更多
In this paper, the brazing mechanism of LY12 aluminum alloy at middle range temperature was presented. The CsF-AlF_3 non-corrosive flux was utilized to remove the complex oxide film on the surface of LY12 aluminum all...In this paper, the brazing mechanism of LY12 aluminum alloy at middle range temperature was presented. The CsF-AlF_3 non-corrosive flux was utilized to remove the complex oxide film on the surface of LY12 aluminum alloy. The results revealed that the oxide film was removed by the improved CsF-AlF_3 flux accompanied with the occurrence of reaction as well as dissolution and the compounds CsF played an important role to remove the oxide film. Actually, the high activity of flux, say, the ability to remove the oxide film, was due to the presence of the compounds, such as NH_4F,NH_4AlF_4 and composite molten salt. The production of HF was the key issue to accelerate the reaction and enhance to eliminate the oxide film by dissolution. It was found that the rare earth element La at small percentage was not enriched at the interface. Moreover, the rare earth fluoride enhanced the dissolution behavior.展开更多
To pre-compress the disk-shaped LY12 samples along the radial direction can be done with the aid of overstress assembly by heating or by mechanical clamping, which can also generate the deviatoric stress fields under ...To pre-compress the disk-shaped LY12 samples along the radial direction can be done with the aid of overstress assembly by heating or by mechanical clamping, which can also generate the deviatoric stress fields under different states. The spallation signals of these pre-compressed samples are measured by VISAR in the light-gas gun shock experiments. The experimental results show that even under the same impact velocity, the pullback amplitudes of the velocity at the free surface of the sam- pies vary significantly. According to the experimental data, we propose a distinct concept that the material spallation strength is closely related to the deviatoric stress fields in the material. Based on the numerical simulation, we develop a damage con- stitutive model, which reveals that the deviatoric stress reduces the tensile threshold of the void growth. The numerical inves- tigations also demonstrate that the spallation strength decreases as pre-compression increases. The experimental idea proposed in this paper can also be used to study the spallation process in other structures.展开更多
基金The authors wish to acknowledge the financial supports of the National Key Basic Research Foundation of China(Grant No.G1999065001)the National Natural Science Foundation of China(Grant No.50071054)the State Key Laboratory for Corrosion and Protection of Metals(China).
文摘The electrochemical features of commercial airfrarne material, Al alloy LY12, in 0.349mol/L neutral sodium chloride (NaCl) and sodium sulfate (NazSO^) solutions were investigated by electrochemical impedance spectroscopy (EIS) and potentiody-namic polarization techniques. The microstructure of the as-tested samples was studied by scanning electron microscopy. The results show that the Nyquist plots of LY12 at different immersion time displayed different features, indicating that the Cl- ions elevate the corrosion rate and inhibit the repassivation of a metastable pit. It also shows that the corrosion product of LY12 formed in SO42- solution isn't easy to dissolve, and it will cover the surface of working electrode in the electrolyte. SEM images indicate that the corrosion apparent area and pit number of LY12 in NaCl solution are greater than that in Na2SO4 solution.
文摘In this paper, the brazing mechanism of LY12 aluminum alloy at middle range temperature was presented. The CsF-AlF_3 non-corrosive flux was utilized to remove the complex oxide film on the surface of LY12 aluminum alloy. The results revealed that the oxide film was removed by the improved CsF-AlF_3 flux accompanied with the occurrence of reaction as well as dissolution and the compounds CsF played an important role to remove the oxide film. Actually, the high activity of flux, say, the ability to remove the oxide film, was due to the presence of the compounds, such as NH_4F,NH_4AlF_4 and composite molten salt. The production of HF was the key issue to accelerate the reaction and enhance to eliminate the oxide film by dissolution. It was found that the rare earth element La at small percentage was not enriched at the interface. Moreover, the rare earth fluoride enhanced the dissolution behavior.
基金supported by the National Natural Science Foundation of China (Grant No. 10772165)the CAEP Foundation for Basic Research (Grant No. 2005R0802)
文摘To pre-compress the disk-shaped LY12 samples along the radial direction can be done with the aid of overstress assembly by heating or by mechanical clamping, which can also generate the deviatoric stress fields under different states. The spallation signals of these pre-compressed samples are measured by VISAR in the light-gas gun shock experiments. The experimental results show that even under the same impact velocity, the pullback amplitudes of the velocity at the free surface of the sam- pies vary significantly. According to the experimental data, we propose a distinct concept that the material spallation strength is closely related to the deviatoric stress fields in the material. Based on the numerical simulation, we develop a damage con- stitutive model, which reveals that the deviatoric stress reduces the tensile threshold of the void growth. The numerical inves- tigations also demonstrate that the spallation strength decreases as pre-compression increases. The experimental idea proposed in this paper can also be used to study the spallation process in other structures.
