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Journal of Chemistry
Volume 2018, Article ID 4262860, 8 pages
https://doi.org/10.1155/2018/4262860
Research Article

Stress Corrosion Cracking of a Forged Mg-Al-Zn Alloy with Different Surface Conditions

Aerospace Research Institute of Materials and Processing Technology, Beijing 100076, China

Correspondence should be addressed to Fengjuan Liu; moc.qq@623721853

Received 25 October 2017; Revised 2 March 2018; Accepted 23 April 2018; Published 14 May 2018

Academic Editor: Mohamed Azaroual

Copyright © 2018 Zhongwei Yin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Stress corrosion cracking (SCC) of a forged Mg-Al-Zn magnesium alloy with different surface conditions was studied by the four-point bending test and alternate immersion test in NaCl solution. The results showed that the bare Mg-Al-Zn magnesium alloy has low susceptivity to SCC, and no abrupt rupture happened after the immersion test for 5 days under an initial stress load of 0.15–0.75σ0.2. With microarc oxidation (MAO) coating, corrosion resistance was enhanced, but more surface cracks were induced, and microcracks could be detected inside corrosive pits when the load was 0.75σ0.2, which is similar to the bare alloy. The composite coating totally avoided both SCC and corrosion. The low susceptivity of the forged AQ80M alloy to SCC should be attributed to the fine grain size and even distribution of secondary phases around the grain boundary.