热处理制度对含Yb航空铝合金电化学腐蚀行为的影响

Influence of heat treatments on electrochemical corrosion behaviours of aircraft Al alloy with Yb micro-alloy

采用开路电位-时间曲线以及循环极化曲线研究了不同时效制度对Al-6.2Zn-2.3Mg-2.3Cu-0.16Zr-0.18Cr-0.3Yb合金(质量分数,%)在10 mmol/L NaCl+0.1mol/L Na_2SO_4溶液中的电化学腐蚀性能的影响。结果表明:不同时效耐局部腐蚀与应力腐蚀的能力由强至弱的顺序依次为T76+T6、T77、T76、T6。结合硬度和电导率测试发现,与常规T77相比,过时效再时效T76+T6处理的铝合金同时具备更优异的耐蚀和强度性能。并系统讨论了点蚀电位(φ_(pit))、自腐蚀电位(φ_(corr))、再钝化电位(φ_(rep))以及电位差值(φ_(rep)-φ_(corr),φ_(pit)-φ_(corr),φ_(pit)-φ_(rep))作为腐蚀判据的可行性和局限性。

The effects of heat treatments on electrochemical corrosion behaviours of Al-6.2Zn-2.3Mg-2.3Cu-0.16Zr- 0.18Cr-0.3Yb alloy (mass fraction, %) in 10 mmol/L NaCl + 0.1mol/L Na2SO4 solution were investigated by open circuit potential and cyclic polarization curve. The results show that the localized corrosion and stress cracking corrosion resistance of various alloys with different ageing processes is in the following order: T76+T6>T77≈T76>T6. Together with the results of hardness and conductivity characterization, it can be found that, compared to those of the conventional T77 ageing, the novel three-step ageing T76+T6 shows the combination of better corrosion resistance and higher strength property. In addition, the suitability and limitations of using pitting potential (φpit), corrosion potential (φcorr), repassivation potential (φrep) and potential differences (φrep?φcor,φpit?φcorr,φpit?φrep) as the corrosion criteria were discussed in detail.