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MM: Fachverband Metall- und Materialphysik

MM 26: Poster Session

MM 26.77: Poster

Dienstag, 23. März 2010, 14:45–16:30, Poster C

Segregation stabilization of nanocrystalline binary alloys at low solute concentrations — •Lionel Kroner and Carl E. Krill III — Institute of Micro and Nanomaterials, Ulm University, Ulm, Germany

Although enhanced properties are predicted for the nanocrystalline state of many materials, the technological exploitation of such improvements generally requires long-term stability of the microstructure at room temperature and short-term stability during processing (e.g. hot pressing, if highly dense bulk samples must be produced from powders). Therefore, effective strategies must be developed to suppress the strong driving force for grain growth that is always present in nanocrystalline materials owing to the very small average grain size. The deliberate addition of an atomic species that segregates to the grain boundaries has already been shown to impart a dramatic improvement in the thermal stability of nanocrystalline Pd powders alloyed with Zr [1]. Can this approach be extended to other materials systems? To answer this question, we prepared a variety of Ni-based and Fe-based nanocrystalline alloys by ball milling elemental powders with small amounts of Zr, Ti, Mo or Co. The higher the segregation tendency, the stronger we expect the inhibiting effect of the solute species to become on grain growth. Using x-ray diffraction, we tested this hypothesis by examining the thermal stability of the samples as a function of annealing temperature, solute concentration and enthalpy of segregation.

[1] C. E. Krill III, H. Ehrhardt and R. Birringer, Z. Metallkd. 96 (2005) 1134–1141.