Journal
INTERMETALLICS
Volume 86, Issue -, Pages 126-133Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.intermet.2017.03.022
Keywords
Solidification; Peritectic reaction; TiAl alloys; Dendrite fragmentation
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Grain size evolution for gamma-TiAl based alloys with aluminum content ranging from 43 to 52 at.% were cast at constant superheat and characterized. Experiments show that the sooner the peritectic phase transition occurs, the finer are the equiaxed grains. An accurate estimate of the number of surviving dendrite fragments and fragmentation rate is performed, which can be used to predict the position of the columnar-to-equiaxed transition in the cast ingots. For alloys solidifying with the beta pro-peritectic primary phase, the fragmentation rate significantly increases when the onset of the peritectic reaction is earlier. A mechanism based on the peritectic reaction is proposed for the observed grain refinement and is discussed on the basis of the fluid flow, mushy zone permeability and the influence of the peritectic reaction. (C) 2017 Elsevier Ltd. All rights reserved.
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