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

Journal Article · Sat Mar 15 04:00:00 EST 1997 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(96)00438-1· OSTI ID:464802

Busse, P; Meissen, F ^[1]

---

1. ACCESS e.V., Aachen (Germany)

Intermetallic compounds are interesting materials for structural, electro-magnetic, chemical or metallurgical applications. They often result from solidification via the peritectic reaction. Because of their low density, high melting point and the resistance in creeping and oxidation, titanium aluminides are most promising high-temperature materials. During isothermal cooling, the properitectic {alpha}-phase solidifies first. At the peritectic temperature, this phase reacts with the melt L and forms the peritectic {gamma}-phase ({alpha}-Ti + L {yields} {gamma}-TiAl). Because the resulting {gamma}-phase envelops the primary {alpha}-phase, further growth of {gamma} is controlled by solid-state-diffusion through the {gamma}-phase. This leads to a relatively coarse microstructure of the two solid-phases causing unsatisfying properties in relation to strength and ductility. In contrast to the predicted axial aligned structure of coupled growth, alternating layers of properitectic and peritectic phase perpendicular to the growth direction were observed. Theoretical predictions for coupled growth in peritectic systems require a narrow solidification interval and almost equal and approximately horizontal slopes of the {alpha}-liquidus line and {gamma}-lines. Diffusion length is thus minimized and the nucleation of the peritectic phase directly from the melt is suppressed. These requirements are met in the TiAl-System.

• OSTI ID: 464802
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 6 Vol. 36; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
DIFFUSION
INTERMETALLIC COMPOUNDS
NUCLEATION
PHASE TRANSFORMATIONS
SOLIDIFICATION
TITANIUM ALLOYS