Microstructural stability of the intermetallic Ti-45Al-2W-0.5Si-0.5B in the 800-980 °C temperature range

gamma-TiAl intermetallic Ti-45Al-2W-0.5Si-0.5B was exposed in the temperature range of 800-980 degreesC, well over its intended application range, for up to 1000 h to test its thermal stability limit. It was found that, the fine alpha(2) laths could be broken down by growth of equiaxed gamma grains, transformation of alpha(2) to B2 phase, and coalescence of alpha(2) laths. With increasing of temperature, needle-like B2 phase became spheral, and its volume fraction increased due to the transformation Of alpha(2) to B2 phase. Addition of boron was demonstrated to be beneficial to the thermal stability of the lamellar structure, by the way of comparison to its boron-free counterpart ABB-2 alloy. Subsurface evolution during long-term aging was also investigated. (C) 2002 Published by Elsevier Science B.V.