The impact of high current densities on the microstructure of nanocrystalline iron-based alloys and related effects during spark plasma sintering of these alloys

Topic

In this project the stability of the nanocrystalline structure of metallic alloys subjected to high current densities will be studied. Interstitial, nanocrystalline iron based alloys (iron with carbon, oxygen and boron) are prepared as thin films on silicon by sputtering and used as model systems to measure grain size, grain boundary segregation and phase separation as a function of electric current density.

Because of the large difference in mobilities between interstitials and Fe-atoms, two separate regimes with accompanying changes of microstructure are expected. The same model alloys will also be prepared as nanocrystalline powders by ball milling and compacted via the field assisted sintering technique or spark plasma sintering (FAST/SPS) and compared with the thin film results. The technological aim is to obtain useful bulk nanocrystalline iron based alloys (nanocrystalline steels) at low enough temperatures where grain growth is suppressed.

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