用电化学实验、浸泡实验与慢应变速率拉伸实验研究铸造AZ91 镁合金在不同浓度比例的CO32-/HCO3-溶液体系中的应力腐蚀(SCC)行为。结果表明，随着溶液pH值的升高，AZ91 镁合金的应力腐蚀敏感性降低。点蚀是AZ91镁合金在该实验体系下的裂纹萌生源，随着实验时间的延长，萌生于点蚀底部的微裂纹会逐渐扩展形成主裂纹，主裂纹靠吞并其前端的微裂纹向前扩展，直至发生SCC失效。
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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