Directly correlated transmission electron microscopy and atom probe tomography of grain boundary oxidation in a Ni–Al binary alloy exposed to high-temperature water

Intergranular oxidation of a Ni–4Al alloy exposed to hydrogenated, high-temperature water was characterized using directly correlated transmission electron microscopy and atom probe tomography. These combined analyses revealed that discrete, well-separated oxides (NiAl2O4) precipitated along grain boundaries in the metal. Aluminum was depleted from the grain boundary between oxides and also selectively from one side of the grain boundary. The discrete oxide morphology, disconnected from the continuous surface oxidation, suggests intergranular solid-state internal oxidation of Al.

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