Effect Of Stress On Intergranular Corrosion Of 2024 Al Alloy

Intergranular corrosion(IGC)of aluminum alloys mostly only analyzes the environmental factors and grain boundary precipitates.In contrast,the study on the effect of the grain boundary characteristics on IGC of aluminum alloy under stress is less.That is to study the corrosion resistance of different types of grain boundaries,and to get excellent corrosion resistance of grain boundaries,thus providing a scientific and experimental basis by using the deformation heat treatment process to enhance the corrosion resistance of material.In this paper,2024 Al alloy was chosen as the research material.The GBCD of2024 Al alloy under different heat treatment conditions were studied by electron backscatter diffraction(EBSD),and the percent contents of the grain boundaries such as low angle boundary(?1),twin boundary(?3),other low coincidence site lattice boundary(?5-?29)and random grain boundary(R)were obtained.Intergranular corrosion(IGC)tests were carried out according to ASTM G110-9.The corrosion morphologies of 2024 Al alloys under different heat treatment conditions were observed by optical microscope to get the correlation between grain boundary corrosion sensitivity and GBCD.The following results were obtained:The proportions of different type grain boundaries in air-cooled,water-quenched,under-aged,peak-aged and over-aged 2024 Al alloy samples ranked from less to more were: ?3<?1<?5-?29<R.The IGC sensitivity of the 2024 Al was investigated immersed for 6 h without any stress.The results showed that corroded proportions of different type grain boundaries in the air-cooled,under-aged,peak-aged and over-aged samples from low to high was?1<?3<?5-?29<R,and the corresponding proportion of corroded grain boundarieswere 12.29%,14.04%,28.79% and 15.45%,respectively.IGC sensitivity from low to high was as follows: air-cooled<under-aged<over-aged<peak-aged.The effect of stress on the IGC sensitivity was investigated.Under the stress of 170 MPa,the IGC sensitivity of the air-cooled,under-aged,peak-aged and over-aged 2024 Al samples from low to high was ?1<?3<?5-?29<R,and the relative proportions of corroded grain boundaries corroded for 6 h were 19.41%,18.37%,34.91% and 31.34%,respectively.Under the stress of 340 MPa,the IGC sensitivity for the samples after air-cooled,under-aged,peak-aged and over-aged treatment from low to high was?1<?3<?5-?29<R.The proportion of corroded grain boundaries immersed for 6 h were 25.57%,23.49%,38.22% and 37.66%,respectively.When the stress increased from 0 to 340 MPa,the corroded proportions of grain boundaries in the air-cooled,under-aged,peak-aged and over-aged 2024 Al samples increased by 108.06%,67.31%,32.75 and 143.75%,respectively.