3 mm thick 7050-T7451 aluminum alloy joint was obtained by friction stir welding, and the two-step aging treatment was performed at 121 ℃ × 5 h + 163 ℃× 27 h after welding. Microstructure, hardness profile...3 mm thick 7050-T7451 aluminum alloy joint was obtained by friction stir welding, and the two-step aging treatment was performed at 121 ℃ × 5 h + 163 ℃× 27 h after welding. Microstructure, hardness profiles and stress corrosion sensitivity of the joint were measured and studied. The results indicate that through the two-step aging, the grain size is coarsened, the age-hardening precipitates and PFZ become wider at the same time, which results in the discontinuous grain boundary;the microhardness of the FSW joints decreased, but the heat-affected zone significantly narrowed, which increased the uniformity of the microhardness of the FSW joints;and the two-stage aging effectively reduced the stress corrosion sensitivity of the FSW joints. The joints with aging treatment were not broken after 60 days,however all the joints without aging treatment were broken within 1 day.展开更多
The effect of compressive residual stress on the reactivity of carbon steel in a neutral chloride solution was investigated by means of potentiodynamic polarization and local electrochemical measurement with scanning ...The effect of compressive residual stress on the reactivity of carbon steel in a neutral chloride solution was investigated by means of potentiodynamic polarization and local electrochemical measurement with scanning electrochemical microscope（SECM）. Meanwhile, X-ray diffraction, as a nondestructive technique, was employed to determine the levels of residual stress in near-surface layers of carbon steel specimen. The results show that the resi- dual stress existed in the specimen fell into the category of compressive residual stress which was inversely propor- tional to the corrosion sensitivity of carbon steel specimen. By using I/I3 couple as a redox mediator in the current feedback mode of SECM measurements, the Faradaic current on Pt tip, which was relevant to the rate of the I3- ion reduction, fell with the increase of compressive residual stress. The correlation between compressive residual stress and heterogeneous electron transfer rate has been proposed based on the inference of the localized electrochemical reactions occurred on the specimen surface,展开更多
基金National Natural Science Foundation of China (51774047)Beijing Great Wall Scholars Training Program(CIT&TCD20170309)。
文摘3 mm thick 7050-T7451 aluminum alloy joint was obtained by friction stir welding, and the two-step aging treatment was performed at 121 ℃ × 5 h + 163 ℃× 27 h after welding. Microstructure, hardness profiles and stress corrosion sensitivity of the joint were measured and studied. The results indicate that through the two-step aging, the grain size is coarsened, the age-hardening precipitates and PFZ become wider at the same time, which results in the discontinuous grain boundary;the microhardness of the FSW joints decreased, but the heat-affected zone significantly narrowed, which increased the uniformity of the microhardness of the FSW joints;and the two-stage aging effectively reduced the stress corrosion sensitivity of the FSW joints. The joints with aging treatment were not broken after 60 days,however all the joints without aging treatment were broken within 1 day.
基金Supported by the National Natural Science Foundation of China（No.51171094）.
文摘The effect of compressive residual stress on the reactivity of carbon steel in a neutral chloride solution was investigated by means of potentiodynamic polarization and local electrochemical measurement with scanning electrochemical microscope（SECM）. Meanwhile, X-ray diffraction, as a nondestructive technique, was employed to determine the levels of residual stress in near-surface layers of carbon steel specimen. The results show that the resi- dual stress existed in the specimen fell into the category of compressive residual stress which was inversely propor- tional to the corrosion sensitivity of carbon steel specimen. By using I/I3 couple as a redox mediator in the current feedback mode of SECM measurements, the Faradaic current on Pt tip, which was relevant to the rate of the I3- ion reduction, fell with the increase of compressive residual stress. The correlation between compressive residual stress and heterogeneous electron transfer rate has been proposed based on the inference of the localized electrochemical reactions occurred on the specimen surface,
