Coupled peritectic growth of the {alpha}- and {gamma}-phases in binary titanium aluminides

Book · Tue Dec 31 04:00:00 EST 1996

OSTI ID:479261

Meissen, F; Busse, P; Laakmann, J ^[1]

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1. 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
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
EUTECTICS
EXPERIMENTAL DATA
INTERMETALLIC COMPOUNDS
LAMELLAE
LIQUID METALS
MICROSTRUCTURE
PHASE DIAGRAMS
SOLIDIFICATION
TITANIUM ALLOYS