[Kovove materialy - Metallic materials]
    Fri - March 29, 2024 - 07:51 No. of hits : 1736639 ISSN 1338-4252 (online) ISSN 0023-432X (printed)
© Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Bratislava, Slovak Republic

VOLUME 45 (2007), Issue 5

Estimation of high temperature phase equilibria in directionally solidified intermetallic Ti-45.9Al-8Nb alloy
GABALCOVA, Z., LAPIN., J.
vol. 45 (2007), no. 5, pp. 231 - 240

Abstract
High temperature phase equilibria were studied in directionally solidified (DS) intermetallic Ti-45.9Al-8Nb (at.%) alloy by the means of quench during directional solidification (QDS) experiments, microstructure analysis and differential thermal analysis (DTA). During directional solidification at constant growth rates V ranging from 5.56x10-6 to 1.18x10-4 m s-1 and three measured temperature gradients in liquid at the solid-liquid interface GL of 3.5x103, 5x103 and 8x103 K m-1 the primary solidification phase is identified to be β phase (Ti based solid solution with bcc crystal structure). The microstructural analysis of quenched mushy zones excluded formation of α phase (Ti based solid solution with hcp crystal structure) by a peritectic reaction during directional solidification. Experimentally determined phase transformation sequences L (liquid) → L + β → β → β + α and estimated high temperature phase stability are different from those resulting from thermodynamic calculations using Thermo-Calc software and TiAl database. Due to preferred [001] crystallographic orientation of the β dendrites, lamellar α2 (Ti3 Al)/ γ(TiAl) boundaries in DS ingots are observed to be inclined at the angles of 0° and 45° to the growth direction.

Key words
titanium aluminides, TiAl, crystal growth, phase transformations, microstructure

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Full title of this journal is bilingual: Kovové materiály - Metallic Materials.
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