A study of the determination of grain boundary diffusivity and energy through the thermally grown oxide ridges on a Fe-22Cr alloy surface

Abstract

The grain boundaries (GBs) present in polycrystalline materials are important with respect to materials behaviour and properties. During the transient stage of oxidation, the higher GB diffusivity results in heterogeneous oxidation structures in the form of oxide ridges that emerge along the alloy GBs. In an attempt to delve into the more fundamental aspects of the GBs, such as GB energy, the size of the oxide ridges was quantitatively measured by atomic force microscopy on the post oxidation surface of a Fe-22 wt % Cr alloy after an oxidation exposure at 800 °C in dry air. The GB diffusivity was calculated utilising the ridge size data and the relationship between the GB diffusivity and the GB characteristics was determined. Furthermore, the GB energy was calculated from the GB diffusivity data, also to make comparison with the data available in the literature. The absolute value of the calculated GB energy was quite close to the values reported in the literature. However, compared to the extremely low temperature (0 K) data-set from the literature, the data-set obtained from this study showed much less spread. The smaller variation range may be attributed to the higher temperature condition (1073 K) in this study.

Keywords:

• Grain boundary
• high temperature oxidation
• grain boundary diffusion
• grain boundary energy

Acknowledgement

The authors acknowledge use of the Materials Characterization Facility at Carnegie Mellon University supported by [grant number MCF-677785]. Also, the National Natural Science Foundation of China [grant number 51501231] is acknowledged. The authors would like to thank Professor Gregory S. Rohrer of the Department of Materials Science and Engineering at Carnegie Mellon University for helpful discussions. We also thank Yang Wang, a former graduate student in the Department of Mechanical Engineering at Carnegie Mellon University for the help in the programming for data processing.