|About this Abstract
||2016 TMS Annual Meeting & Exhibition
||Phase Transformations in Multi-component Systems: An MPMD Symposium Honoring Gary R. Purdy
||Effects of Internal Oxidation on Microstructure in Ni Alloy 600
||Brian Langelier, Suraj Y. Persaud, Roger C. Newman, Gianluigi A. Botton
|On-Site Speaker (Planned)
The degradation of Ni-based alloy 600 by internal oxidation involves the inward diffusion of oxygen to preferentially oxidize Cr and Fe solutes. The complex microstructural changes associated with this phenomenon are examined here using electron microscopy and atom probe tomography, and will be discussed in terms of the diffusion behaviours of both solvent and solute elements. Intragranular internal oxidation produces nanometer-scale metal-oxide networks in the sub-surface regions. Volumetric expansion associated with oxidation drives Ni to the surface, where it forms sub-micron-sized metallic nodules. Oxidation originates by Cr2O3 precipitation, but local matrix depletion of Cr and enrichment of Fe around growing Cr2O3 eventually causes FeCr2O4 spinel to form instead. At grain boundaries, accelerated Cr diffusion allows the exclusive formation of Cr2O3, with only minor segregation of other elements. Extensive diffusion induced grain boundary migration is also observed, both at the intergranular oxide, and well below the oxide front.
||Planned: A print-only volume