Crystal growth of TiAl alloys

The growth of TIAl alloys over a range of Al concentrations has been considered for ingots processed by the floating zone technique. For Al-rich alloys, single crystals of gamma-TiAl cannot be grown for compositions below Ti-54 at% Al since a banded microstructure forms due to the limitations imposed by the L+alpha --> gamma peritectic reaction. However, near stoichemetric TiAl crystals can be grown by the traveling solvent method when using a TiAl-Co flux, although optimum processing conditions have not yet been realized. For Ti-rich alloys, evidence of a growth morphology consisting of beta-phase dendrites embedded within a continuous matrix of the peritectic alpha-phase is found for ingots processed up to 200 mm h(-1) The final lamellar orientation of the ingot is then determined by the orientation of the peritectic alpha-phase and not by that of the leading beta dendrites. (C) 1998 Elsevier Science Limited. All rights reserved.