Effect of ageing process on microstructure, corrosion behaviors and mechanical properties of Al-5.6Zn-1.6Mg-0.05Zr alloy

Abstract

The influence of different ageing processes on the microstructure, corrosion behaviors and mechanical properties of extruded Al−5.6Zn−1.6Mg−0.05Zr (wt.%) alloy was studied in this work. The changes of morphology, size and distribution of MgZn₂ precipitate with ageing temperature and time were revealed by optical and electron microscopy. Intergranular corrosion (IGC) and exfoliation corrosion (EXCO) tests were carried out to assess the changes in corrosion susceptibility of the tempered alloy, and some white spots on the surface of the sample aged for longer time were found to be precursors of pits. Electrochemical cyclic polarization test depicted the corrosion behavior under different tempers. Ageing influences on the mechanical behaviors of the alloy were revealed by evaluating its microhardness and tensile strength. The microscopic features of the strengthening phases determined by the ageing procedure directly affect the corrosion resistance and mechanical properties of the alloy.

Keywords

Al-Zn-Mg alloy / microstructure / corrosion behavior / mechanical properties / ageing process

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