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| STRESS CORROSION CRACKING BEHAVIORS OF AS-CAST AZ91 MAGNESIUM ALLOY IN CO32-/HCO3- SOLUTIONS |
| HUANG Fa, CHEN Jian, WANG Jianqiu |
| State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 |
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Abstract The stress corrosion cracking (SCC) behaviors of as-cast AZ91 magnesium alloy in CO32-/HCO3- solutions were investigated by electrochemical test, immersion test and slow strain rate test (SSRT) respectively. The results showed that the stress corrosion cracking sensitivity of as-cast AZ91 alloy in CO32-/HCO3- solutions decreased with the increase of pH values of the solutions. The surface was covered by a film mainly composed of Mg(OH)2 and Al(OH)3. Al(OH)3 could be dissolved in alkaline solutions and AlO2- engendered. Pitting was the main crack source of AZ91 alloy in such solutions. The cracking of β phase also resulted in microcracks in the matrix. Microcracks initiating at the bottom of pitting combined into a main crack. The main crack propagated by coalescence of the existing microcracks ahead until the SCC fracture occurred.
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Received: 28 September 2009
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Corresponding Authors:
WANG Jianqiu
E-mail: wangjianqiu@imr.ac.cn
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