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INFLUENCE OF ALUMINIUM CONTENT AND CASTING TECHNOLOGY
ON THE COLUMNAR-TO-EQUIAXED TRANSITION IN TI-xAL-2CR-2NB ALLOYS
J. Zollingera,b,*, N.T. Reillya,b,c, B. Rouata,b , G. Martinc , D. Daloza,b
a
Université de Lorraine, Institut Jean Lamour, Department of Metallurgy & Materials Science and
Engineering, Parc de Saurupt, F-54011 Nancy, France
b
Laboratory of Excellence on Design of Alloy Metals for low–mAss Structures (’LabEx DAMAS’), France
c
SNECMA Gennevilliers, SAFRAN group, F-92702 Colombes Cedex, France
ABSTRACT
Aluminium content in titanium aluminides has a strong impact on their mechanical properties together with
their microstructure, and particularly with the grain size and the lamellar spacing. This work investigates
the effect of aluminium content (ranging from 43 to 52 at.% Al) on the solidification behaviour of GE
based alloys containing 2 at.% Cr and Nb using different casting technologies involving different
solidification and flow velocities. For alloys solidifying with the (Ti)-phase, the results shows that
increasing the aluminium content decrease the equiaxed grain size in castings. Increasing the liquid flow
also decrease equiaxed the grain size. Using ThermoCalc calculations and a finite-element model, the
experimental number of surviving dendrite fragment is implement in Hunt’s model to predict the
occurrence of the columnar to equiaxed transition (CET). The agreement between experiments and
calculations is good and validate the estimate of dendrite fragments determined from the grain size. The
main mechanism to explain such grain size decrease is based on the peritectic reaction and is discussed
based on pro-peritectic phase fraction and solidification conditions.
KEYWORDS
TiAl alloys, Casting, Microstructure, Solidification