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Kornfeinung borhaltiger Hochtemperatur-Leichtbaulegierungen auf Basis der intermetallischen Phase Gamma-TiAl
Citation Link: https://doi.org/10.15480/882.1078
Other Titles
Grain refinement of boron containing high temperature lightweight alloys based on the intermetallic phase gamma-TiAl
Publikationstyp
Doctoral Thesis
Date Issued
2012
Sprache
German
Author(s)
Advisor
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2012-10-19
TORE-DOI
The grain refinement of boron containing TiAl-based alloys has been investigated under the influence of titanium boride formation in the melt. The determination of crystallographic orientation relationships shows, that titanium borides act as heterogeneous nucleation sites for the beta(Ti) and alpha(Ti) phase. At low boron contents titanium borides form in the melt concurrently with the beta(Ti) phase but prior to the alpha(Ti) phase. In this case the grain refinement of the as cast microstructure is attributed to heterogeneous alpha(Ti) nucleation on titanium borides. The growth morphology of theses borides enhances alpha(Ti) grain refinement since large nucleation sites (in contrast to boride formation at high boron contents) developed. At high boron contents titanium borides form in the melt prior to the alpha(Ti) phase. By using a model calculation the beta(Ti) grain refinement could be simulated based on TiB2 particle size distributions. An optimization of the model shows: (1) the TiB2 particle morphology limits the beta(Ti) grain refinement and (2) the number density of nucleated alpha(Ti) grains is relatively low.
Subjects
grain refinement
nucleation
titanium aluminides
metal physics
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Dissertation_Gosslar_2012_urn.pdf
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