铈离子对高强铝合金应力腐蚀开裂的缓蚀作用

发布时间：2018-04-03 21:02

本文选题：铝合金　切入点：应力腐蚀　出处：《材料工程》2017年05期

【摘要】：基于慢应变速率拉伸实验(SSRT),采用恒电流极化、电化学噪声(ECN)与电化学阻抗(EIS)等方法,研究7A04铝合金在3.5%(质量分数)NaCl水溶液中的应力腐蚀开裂(SCC)行为以及Ce~(3+)对其SCC的缓蚀作用,探讨Ce~(3+)对裂纹孕育与发展过程的抑制机理。结果表明:无论是阳极还是阴极极化,均会促进7A04的SCC倾向,前者增加了裂尖的阳极溶解,后者则加速了裂尖的氢脆效应。Ce~(3+)的加入能延缓7A04的SCC断裂时间,但其有效性仅限于裂纹的萌生阶段。由于Ce~(3+)能够抑制铝合金表面的亚稳态点蚀发育和长大,因而使裂纹的孕育时间显著延长,降低了SCC的敏感性。不过一旦裂纹进入扩展阶段或者试样表面有预裂纹,则由于Ce~(3+)很难迁移到裂纹尖端或在裂尖区难以成膜,不能对裂纹的生长起到有效抑制作用,因而无法降低7A04的SCC发展速率。SEM分析表明7A04铝合金光滑试样SCC主要源于亚稳态或稳态点蚀的诱导作用。
[Abstract]:Based on the slow strain rate tensile test (SSRT), the stress corrosion cracking (SCC) behavior of 7A04 aluminum alloy in 3.5% NaCl aqueous solution and the inhibition effect of Ce~(3 on SCC were studied by means of constant current polarization, electrochemical noise and electrochemical impedance spectroscopy (EIS).The inhibition mechanism of Ce~(3 on the initiation and development of cracks was discussed.The results show that both anode and cathode polarization can promote the SCC tendency of 7A04. The former increases the anodic dissolution of crack tip, while the latter accelerates the hydrogen embrittlement effect of 7A04.But its validity is limited to the crack initiation stage.Because Ce~(3 can inhibit the metastable pitting development and growth of aluminum alloy surface, the incubation time of cracks is significantly prolonged and the sensitivity of SCC is reduced.However, once the crack enters the stage of propagation or there is a pre-crack on the surface of the specimen, it is difficult for Ce~(3 to migrate to the crack tip or to form a film in the crack tip, which can not effectively inhibit the growth of the crack.Therefore, the SCC development rate of 7A04 can not be reduced. SEM analysis shows that the SCC of 7A04 aluminum alloy smooth specimen is mainly due to the induction of metastable or steady-state pitting.
【作者单位】：华中科技大学化学与化工学院材料化学与服役失效湖北省重点实验室;中航工业特种飞行器研究所;湖北文理学院化工与食品学院;
【基金】：国家自然科学基金资助项目(51371087)
【分类号】：TG178

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