Thermally Stability of Nanocrystalline Microstructures
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Date
2009-03-23
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Abstract
Fe based alloys were high energy ball milled to produce supersaturated solid solutions with a nominal grain size of ~10nm. Solutes such as Y, W, Ta, Ni and Zr were selected based on their propensity to grain boundary segregated in Fe. Based on preliminary heat treatments Zr was selected as the solute of choice. Upon further heat treating experiments and microstructural analysis it was found that Zr solute additions of < 4at% could stabilize a nanocrystalline microstructure of <100nm at temperatures in excess of 900oC. This is in stark comparison to pure nanocrystalline Fe which shows coarsening to the micron scale after annealing above 600oC. Reduction in grain boundary energy due to Zr segregation and solute drag are proposed as mechanism responsible for the observed thermal stability.
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Thermal, Iron, Nanocrystalline, Segregation, Solvent, Solute
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PhD
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Materials Science and Engineering
