Desai Choundraj Jahnavi, Kacher Josh
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
Sci Rep. 2022 Feb 2;12(1):1817. doi: 10.1038/s41598-022-05948-8.
Al-Mg alloys undergo sensitization when exposed to elevated temperatures, making them susceptible to intergranular corrosion and stress corrosion cracking. Most of the existing research on microstructure effects on sensitization is centered on the effect of intrinsic grain boundary characteristics such as misorientation angle and coincident site lattice (CSL) values. Very few studies have systematically investigated the influence of extrinsic characteristics such as dislocation density. In this paper, the influence of local microstructure characteristics on the sensitization susceptibility of AA5456 was investigated using in situ optical microscopy corrosion experiments and electron back scattering diffraction analysis. The results show a clear trend between the local geometrically necessary dislocation (GND) density and β phase precipitation, with higher GND densities correlating with higher rates sensitized boundaries. This trend held true even for low angle grain boundaries. These results demonstrate the importance of considering factors beyond grain boundary characteristics in determining susceptibility to sensitization.
铝镁合金在暴露于高温时会发生敏化，使其易受晶间腐蚀和应力腐蚀开裂的影响。现有的关于微观结构对敏化影响的研究大多集中在诸如取向差角和重合位置点阵（CSL）值等固有晶界特征的影响上。很少有研究系统地研究诸如位错密度等外在特征的影响。本文通过原位光学显微镜腐蚀实验和电子背散射衍射分析，研究了局部微观结构特征对AA5456敏化敏感性的影响。结果表明，局部几何必要位错（GND）密度与β相析出之间存在明显的趋势，较高的GND密度与较高的敏化边界速率相关。即使对于低角度晶界，这种趋势也成立。这些结果表明，在确定敏化敏感性时，考虑晶界特征以外的因素非常重要。
