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http://dx.doi.org/10.12656/jksht.2016.29.5.227

Study on High Temperature Phase Transformation and Directional Solidification of TiAl-Nb Alloy  

Park, Jong-Moon (School of Materials Science and Engineering, Kumoh National Institute of Technology (KIT))
Jang, Ho-Seung (School of Materials Science and Engineering, Kumoh National Institute of Technology (KIT))
Kim, Seong-Woong (Titanium department, Korea Institute of Materials Science (KIMS))
Kim, Seung-Eon (Titanium department, Korea Institute of Materials Science (KIMS))
Shon, Je-Ha (Advanced Technology Team, Pohang Institute of Metal Industry Advancemnet (POMIA))
Oh, Myung-Hoon (School of Materials Science and Engineering, Kumoh National Institute of Technology (KIT))
Publication Information
Journal of the Korean Society for Heat Treatment / v.29, no.5, 2016 , pp. 227-233 More about this Journal
Abstract
Phase transformation phenomenon at high temperature was investigated by using designed TiAl-Nb alloys with addition of the ${\beta}$ stabilizer. Examination of dendritic morphologies in arc-melted button ingot could reveal the crystallography of the primary solidification phase. It was found that the addition of ${\beta}$ stabilizer(Nb) shifted the high temperature region of the binary Ti-Al phase diagram to the high Al composition side so that ${\beta}$ phase forms as a primary crystal even at higher Al composition compared with the binary Ti-Al system. The ${\beta}$ was found to be the primary solidification phase for alloys with Al content less than about 52 at.%. The composition of ${\beta}$ solidification in Ti-Al-Nb ternary system could be determined from the partial liquidus projection which was constructed by observing the microstructure of arc-melted buttons. The Ti-46Al-(6, 8)Nb composition was selected for ${\beta}$ solidification and the directional solidification was performed by a floating zone-type DS apparatus at the growth rate 30 mm/hr respectively.
Keywords
TiAl alloy; ${\beta}$ solidification; ${\beta}$ stabilizer; Directional solidification; Lamellar boundary orientation;
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