Al-Zn-Cu-Mg及Al-Cu-Mg在氯化物水溶液中应力腐蚀开裂的扫描电镜断口形貌

本文研究了Al—Zn—Cu—Mg及Al—Mg—Cu在氯化物水溶液中用慢应变速率方法得到的应力腐蚀开裂的扫描电镜断口形貌。结果发现两种铝合金在氯化物水溶液中的应力腐蚀开裂断口复盖着—层腐蚀产物,这层腐蚀产物可以呈现不同的扫描电镜断口形貌,如类似解理的“平滑”形貌,“龟裂泥巴状”形貌等等。遮盖了应力腐蚀开裂固有的真实形貌;应力腐蚀开裂固有的真实形貌是相同的,呈典型的沿晶开裂形貌,盖有腐蚀产物层的形貌则取决于介质pH和电位。因此,应该根据铝合金应力腐蚀开裂固有的真实扫描电镜断口形貌来鉴别铝合金的应力腐蚀。将断口进行化学去膜处理可以得到铝合金应力腐蚀开裂的固有的真实的扫描电镜断口形貌。

Scanning Electron Fractographs of Stress Corrosion Cracking of Al-Zn-Cu-Mg and A1-Cu-Mg in Aqueous Solution Containing Chloride

The scanning electron fractographs of stress corrosion cracking of Al—Zn—Cu—Mg and Al—Cu—Mg in aqueous solution containing chloride were stutied. Stress corrosion cracking was produced by slow strain rate method. It was found that on the stress corrosion cracking surfaces of the two alloys there was a corrosion product layer which showed various different scanning electron fractographs, such as smooth flat feature resembling cleavage fracture, or "mud-crack pattern" and so on. These, howerer,are not the inherent and real morphologic features of stress corrosion cracking which are actually the same for both alloys under all testing conditions and have typical intergranular cracking feature. The morphology of the corrosion product layer depends on pH of the environment and on potential. The inherent and real scanning electron fractographs of stress corrosion cracking of aluminium alloys can be visualized after removal of the corrosion product layers by chemical method.