AL-6XN合金在超临界水中的应力腐蚀研究

采用慢拉伸试验研究了AL-6XN合金在550~650℃、25 MPa超临界水中的应力腐蚀行为,使用扫描电镜观察了材料断口形貌与标距面裂纹分布。结果显示:550℃试验条件下材料表现为穿晶开裂,标距面裂纹很多且分布较均匀,试样边角处出现扇形河流花样;650℃试验条件下材料表现为沿晶开裂,断口呈现典型的冰糖状,标距面裂纹数量大幅减少且集中于断口附近,相应的延伸率和断面收缩率也大幅降低。质子辐照对AL-6XN宏观力学性能影响不大,但导致试样断口的扇形花样(起裂源)数量增加,解理台阶宽度增大。以上结果表明,AL-6XN在超临界工况下具有严重的应力腐蚀开裂敏感性,升高温度和质子辐照会明显提高材料的应力腐蚀敏感性。

Stress Corrosion Cracking Behavior of AL-6XN in Supercritical Water

The stress corrosion cracking (SCC) behavior of AL-6XN alloy in supercritical water with 550-650℃ and 25 MPa was studied by slow strain rate test (SSRT). The facture morphology and gauge surface crack of the specimen were observed by scanning electron microscopy (SEM). In 550℃ test condition, the material presents transgranular cracking. Many uniform distributed cracks appear on the gauge surface, and fan-shaped river patterns appear at the corners on the fracture surface. In 650℃ test condition, the material displays intergranular cracking. The fracture surface reveals typical rock candy pattern, and much fewer cracks appear at the fracture end on the gauge surface. Proton irradiation at 550℃ has little effect on the mechanical property of AL-6XN, but induces more fan-shaped patterns (cracking origins) and wider slipping steps. AL-6XN alloy presents severe SCC sensitivity in supercritical water, which is enhanced by higher temperature and proton irradiation.