应变速率对Al-Zn-Mg合金应力腐蚀性能的影响

Influence of Strain Rates on Stress Corrosion Resistance of Al-Zn-Mg Alloy

摘要: 通过电化学和应力腐蚀试验并结合扫描电镜分析了Al-Zn-Mg合金在3.5 wt% NaCl溶液中的应力腐蚀行为，阐明了应变速率对Al-Zn-Mg合金应力腐蚀性能的影响。研究结果表明，Al-Zn-Mg合金在3.5 wt% NaCl溶液中具有应力腐蚀敏感性；不同应变速率下(10⁻⁴ s⁻¹、10⁻⁶ s⁻¹和10⁻⁷ s⁻¹)的Al-Zn-Mg合金应力腐蚀敏感性的差异来源于腐蚀环境和力学循环作用的程度。当应变速率为10⁻⁶ s⁻¹时，合金具有最高的应力腐蚀敏感指数。当应变速率低于10⁻⁶ s⁻¹时，腐蚀作用占主导位置，冗长的腐蚀时间造成裂纹断面的过度腐蚀，裂纹的扩展受阻，因而合金的应力腐蚀敏感指数稍有下降。当应变速率高于10⁻⁶ s⁻¹时，力学的作用影响更大，裂纹面未充分发生腐蚀，应力作用已导致合金发生快速断裂，从而显著降低了合金的应力腐蚀敏感性。

Abstract: The stress corrosion behavior of Al-Zn-Mg alloy in 3.5 wt% NaCl solution was investigated by elec-trochemical measurements, stress corrosion testing and scanning electron microscopy (SEM). The influence of strain rate on stress corrosion properties of Al-Zn-Mg alloy was revealed. The results showed that the Al-Zn-Mg alloy is sensitive to stress corrosion in 3.5 wt% NaCl solution. There was the highest stress corrosion sensitivity at the strain rate of 10⁻⁶ s⁻¹. However, corrosion and me-chanical factors have different effects during stress corrosion sensitivity index of Al-Zn-Mg alloy at the different rates (10⁻⁴ s⁻¹, 10⁻⁶ s⁻¹ and 10⁻⁷ s⁻¹). When the strain rates were lower than 10⁻⁶ s⁻¹, enough long corrosion time caused corrosion crack in this strain rate range. The stress corrosion crack propagation is limited. So, slight decrease of the stress corrosion sensitivity occurs. As the strain rates were higher than 10⁻⁶ s⁻¹, the stress corrosion susceptibility of Al-Zn-Mg alloy was low clearly. In this strain rate, the influence of mechanical factors on stress corrosion is greater than that of corrosion factors, which mainly leads to mechanical fracture of the Al-Zn-Mg alloy.