Influence of aging treatment on corrosion behavior of extruded 2195 Al-Li alloy
The 2195 Al-Li alloy was processed by under-aging(UA),peak-aging(PA),double-aging(DA)and retrogression re-aging(RRA)treatments,and the microstructure,intergranular corrosion(IGC),exfoliation corrosion(EXCO)and stress corrosion cracking(SCC)behaviors were observed and discussed.The results show that the sequence of IGC and EXCO resistance is:RRA＞UA＞DA＞PA.The low corrosion resistance of PA and UA is mainly caused by the continuous precipitation of Ti phases at grain boundaries to form continuous corrosion channels,while the interruption of corrosion channels caused by coarse and discontinuous T1 phases and wider precipitate free zone is the reason for the best corrosion resistance of RRA.The RRA alloy exhibits the best SCC resistance,and the order of SCC resistance is:RRA＞DA＞UA＞PA.The discontinuous precipitation of intergranular T1 phases promotes the propagation of corrosion cracks across grain boundaries,thereby improving the SCC resistance.
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