The exfoliation corrosion behavior of a novel Al-Li alloy treated by T6- and T8-peak ageing was studied by electrochemical impedance spectroscopy(EIS) technique. The surface morphology of corroded samples was examined...The exfoliation corrosion behavior of a novel Al-Li alloy treated by T6- and T8-peak ageing was studied by electrochemical impedance spectroscopy(EIS) technique. The surface morphology of corroded samples was examined by scanning electron microscope(SEM). The microstructure of un-corroded samples was observed by transmission electron microscope(TEM). At early stage of immersion in EXCO, EIS plots of the two differently processed samples are composed of a capacitive arc in the high frequency range and an inductive loop in the low frequency range. Inductive loop disappears with the increasing of immersion time and two capacitive arcs appear. T6-treated alloy has higher exfoliation susceptibility than T8-treated one, suggested by different exfoliation starting time, which is 23 h and 27 h respectively. T1 phase and equilibrium precipitate at the grain boundary of T6-treated alloy are larger in amount and size than those of T8-treated alloy. This is the main reason for the higher exfoliation susceptibility of T6-treated alloy.展开更多
The effects of aging on mechanical properties, intergranular corrosion and exfoliation corrosion behaviors of a 2197 type Al-Li alloy were investigated, and the mechanisms were studied through microstructure observati...The effects of aging on mechanical properties, intergranular corrosion and exfoliation corrosion behaviors of a 2197 type Al-Li alloy were investigated, and the mechanisms were studied through microstructure observation and electrochemical measurement of simulated bulk phase. The main strengthening precipitates of the alloy aged at 175 ℃ and 160 ℃ are δ′ and T1. T1 precipitation in the alloy aged at 160 ℃ is delayed, which results in its slower age strengthening and over-aging behavior than the alloy aged at 175 ℃. Meanwhile, aging temperature of 160 ℃ causes more uniform distribution and finer size of T1, resulting in its better strengthening effect. As aging time and aging temperature are increased, the size of T1 at grain boundaries and the width of PFZ along grain boundaries are increased, leading to an increase in the susceptibility to intergranular corrosion and exfoliation corrosion. It is suggested that better comprehensive properties can be obtained when the alloy is aged at 160 ℃.展开更多
The influence of forging and aging treatment on mechanical properties and microstructure of large size prestretched thick plate of 7B04 aluminium alloy was investigated through tensile test, corrosion test, transmissi...The influence of forging and aging treatment on mechanical properties and microstructure of large size prestretched thick plate of 7B04 aluminium alloy was investigated through tensile test, corrosion test, transmission electronic microcopy(TEM) and energy dispersive spectrum(EDS) analysis. The results show that the properties of plate performed extra forging (FSR technology) are much higher than those of plate without forging (CSR technology). T7451 temper is preferred to resisting corrosion than T651 temper due to a wide PFZ and discontinuous grain boundary precipitates.展开更多
文摘The exfoliation corrosion behavior of a novel Al-Li alloy treated by T6- and T8-peak ageing was studied by electrochemical impedance spectroscopy(EIS) technique. The surface morphology of corroded samples was examined by scanning electron microscope(SEM). The microstructure of un-corroded samples was observed by transmission electron microscope(TEM). At early stage of immersion in EXCO, EIS plots of the two differently processed samples are composed of a capacitive arc in the high frequency range and an inductive loop in the low frequency range. Inductive loop disappears with the increasing of immersion time and two capacitive arcs appear. T6-treated alloy has higher exfoliation susceptibility than T8-treated one, suggested by different exfoliation starting time, which is 23 h and 27 h respectively. T1 phase and equilibrium precipitate at the grain boundary of T6-treated alloy are larger in amount and size than those of T8-treated alloy. This is the main reason for the higher exfoliation susceptibility of T6-treated alloy.
基金Project(50401012) supported by the National Natural Science Foundation of China Project supported by the Key Pro gram of the 10th Five year Plan of China Project supported by the Scientific Research Foundation of Central South University
文摘The effects of aging on mechanical properties, intergranular corrosion and exfoliation corrosion behaviors of a 2197 type Al-Li alloy were investigated, and the mechanisms were studied through microstructure observation and electrochemical measurement of simulated bulk phase. The main strengthening precipitates of the alloy aged at 175 ℃ and 160 ℃ are δ′ and T1. T1 precipitation in the alloy aged at 160 ℃ is delayed, which results in its slower age strengthening and over-aging behavior than the alloy aged at 175 ℃. Meanwhile, aging temperature of 160 ℃ causes more uniform distribution and finer size of T1, resulting in its better strengthening effect. As aging time and aging temperature are increased, the size of T1 at grain boundaries and the width of PFZ along grain boundaries are increased, leading to an increase in the susceptibility to intergranular corrosion and exfoliation corrosion. It is suggested that better comprehensive properties can be obtained when the alloy is aged at 160 ℃.
基金Project(2003AA331100) supported by Commission of Science Technology and Industry for National Defence
文摘The influence of forging and aging treatment on mechanical properties and microstructure of large size prestretched thick plate of 7B04 aluminium alloy was investigated through tensile test, corrosion test, transmission electronic microcopy(TEM) and energy dispersive spectrum(EDS) analysis. The results show that the properties of plate performed extra forging (FSR technology) are much higher than those of plate without forging (CSR technology). T7451 temper is preferred to resisting corrosion than T651 temper due to a wide PFZ and discontinuous grain boundary precipitates.
