Abstract The ASTM G67 Nitric Acid Mass Loss Test (NAMLT) is not a universally accurate proxy for intergranular stress corrosion cracking (IG-SCC) susceptibility in Al-Mg alloys. This study aims to understand this discrepancy via an electron backscatter diffraction (EBSD) and ammonium persulfate etching/overlay analysis to characterize the linear grain boundary β coverage (LGBBC). Testing at three NAMLT levels of AA5083-H131, AA5083-H116, AA5083-SHTQ, and AA5456-H116 derived from fracture specimens demonstrates that LGBBC is a more accurate metric to describe the IG-SCC susceptibility, however the correlation degrades for materials with divergent yield strengths. These results provide insights necessary to improve upon ASTM G67.

中文翻译：

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不同成分和回火的 Al-Mg 合金中的 Beta 相分布

摘要 ASTM G67 硝酸质量损失测试 (NAMLT) 并不是 Al-Mg 合金晶间应力腐蚀开裂 (IG-SCC) 敏感性的普遍准确代表。本研究旨在通过电子背散射衍射 (EBSD) 和过硫酸铵蚀刻/覆盖分析来了解这种差异，以表征线性晶界 β 覆盖率 (LGBBC)。在来自断裂试样的 AA5083-H131、AA5083-H116、AA5083-SHTQ 和 AA5456-H116 三个 NAMLT 水平上的测试表明，LGBBC 是描述 IG-SCC 敏感性的更准确的度量，但是对于具有发散性的材料，相关性会降低屈服强度。这些结果为改进 ASTM G67 提供了必要的见解。