[Kovove materialy - Metallic materials]
    Mon - November 11, 2024 - 02:32 No. of hits : 1797366 ISSN 1338-4252 (online) ISSN 0023-432X (printed)
© Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, Bratislava, Slovak Republic

VOLUME 51 (2013), Issue 2

Effect of solidification parameters on microsegregation behaviour of main alloying elements in a peritectic TiAl based alloy
KLIMOVA, A., LAPIN, J., PELACHOVA, T., NOSKO, M.
vol. 51 (2013), no. 2, pp. 89 - 99
DOI: 10.4149/km_2013_2_89

Abstract
The effect of solidification parameters such as growth rate V and temperature gradient GL on microsegregation behaviour of main alloying elements in peritectic Ti-44Al-5Nb-0.2B-0.2C (at.%) alloy was studied. Samples for microsegregation study were prepared by quench during directional solidification (QDS) at various combinations of V and GL. The studied alloy solidifies with β (Ti-based solid solution with cubic crystal structure) primary solidification phase and undergoes L + β → α peritectic transformation. The energy-dispersive spectrometry (EDS) analyses and calculated effective distribution coefficients keff for Al, Ti and Nb confirm that the alloying elements such as Ti and Nb segregate predominantly into the β dendrites and Al into the interdendritic liquid during directional solidification. Formation of the peritectic α-phase (Ti-based solid solution with hexagonal crystal structure) leads to an intensive back-diffusion of the alloying elements. Boron segregates into interdendritic liquid where it forms (Ti,Nb)B particles with ribbon-like morphology. Severity of microsegregation expressed by segregation deviation parameter σmAL for aluminium decreases with increasing growth rate V in the mushy zone and only slightly increases below the mushy zone. Moderate decrease of σmAL with the increase of GL is observed at all measured positions except the position located close to the dendrite tip.

Key words
titanium aluminides, TiAl, solidification, energy-dispersive spectrometry, microsegregation

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