Journal
ACTA MATERIALIA
Volume 58, Issue 20, Pages 6744-6751Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2010.08.040
Keywords
Titanium aluminides; Casting; Grain refining; Edge-to-edge matching; Crystal growth
Funding
- DFG (German Research Foundation) [SPP1296]
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A crystallographic model is used to predict the nucleation potencies of TiB2 particles during solidification of TiAl-based alloys. Two nucleation scenarios are investigated. In scenario 1, primary TiB2 grows in the melt before formation of the body-centred cubic beta phase. In scenario 2, secondary TiB2 precipitates after the first beta phase but before formation of the hexagonal close-packed alpha phase. The model predicts high alpha and beta nucleation potencies of TiB2 in both scenarios. However, pre-existing beta grains in scenario 2 are predicted to be preferred alpha nucleation sites. The experimentally observed beta refinement by primary TiB2 agrees with the model predictions. Grain refinement in scenario 2 is attributed to alpha nucleation on beta, which is interleaved with secondary TiB2. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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