Coupled peritectic growth of the {alpha}- and {gamma}-phases in binary titanium aluminides
- ACCESS e.V., Aachen (Germany)
Coupled growth during three phase equilibrium solidification is well known from directionally solidified eutectic systems, and was recently generated in monotectic systems. Several theories predict a stationary peritectic reaction and coupled growth of the properitectic and the peritectic phases therefore should be possible. In spite of these theories coupled growth has not been observed up to now. The TiAl system was selected for further investigation on this topic because of its technical relevance and the fact that it meets the condition mentioned for coupled growth. In a Bridgman laboratory furnace, TiAl with 53.4 at.% Al was directionally solidified with solidification rates v between 0.025 mm/min and 0.1 mm/min and a temperature gradient up to 20 K/mm. The resulting microstructures, analyzed using optical and scanning microscopy with EDX and WDX, consist of two phases parallel to the growth direction. At v = 0.05 to 0.1 mm/min, the alloy solidifies as properitectical {alpha}, which subsequently eutectoidally transforms to a substructure of {alpha}{sub 2}-Ti{sub 3}Al and {gamma}-TiAl, and peritectic {gamma}. The lamellar {alpha}{sub 2}/{gamma}-substructure is oriented parallel to the growth direction. The experimental results were compared with the existing theoretical models of a stationary peritectic reaction and the possibility of metastable eutectic growth was discussed.
- Sponsoring Organization:
- Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)
- OSTI ID:
- 479261
- Report Number(s):
- CONF-951155-; ISBN 1-55899-301-0; TRN: IM9725%%22
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 27 Nov - 1 Dec 1995; Other Information: PBD: 1996; Related Information: Is Part Of Thermodynamics and kinetics of phase transformations; Im, J.S. [ed.] [Columbia Univ., New York, NY (United States)]; Park, B. [ed.] [Georgia Inst. of Tech., Atlanta, GA (United States)]; Greer, A.L. [ed.] [Cambridge Univ. (United Kingdom)]; Stephenson, G.B. [ed.] [Argonne National Lab., IL (United States)]; PB: 697 p.; Materials Research Society symposium proceedings, Volume 398
- Country of Publication:
- United States
- Language:
- English
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