Revealing the evolution of microstructure, mechanical property and corrosion behavior of 7A46 aluminum alloy with different ageing treatment

摘要

Mechanical property and corrosion behavior of 7A46 aluminum alloy under peak-ageing (T6), doubleageing (DA) and pre-ageing (PA) followed by double-ageing (PA-DA) are systematically investigated. The hardness and strength of aged 7A46 alloy follows an order of T6> PA-DA > DA and the rank of corrosion resistance is PA-DA > DA > T6. The small size and dispersed distribution of matrix precipitates (MPs) lead to the high hardness and strength of T6 alloy, and low hetero-phase potential differences and less formation probability of corrosion galvanic couples enhance the corrosion resistance of PA-DA alloy. Intergranular corrosion (IGC) test results reveal that considerable potential differences promote the formation rate and the quantity of corrosive-batteries between the matrix and grain boundary precipitations (GBPs) or precipitate-free zones (PFZs). The exfoliation corrosion (EXCO) rate and the weight gain trend of corrosion products are related to the oxide film formation rate and corrosion products accumulation. Localized anodic dissolution and hydrogen embrittlement can induce the stress cracking corrosion (SCC). (c) 2019 Elsevier B.V. All rights reserved.