B2 precipitates and distribution of W in a Ti–47Al–2W–0.5Si alloy

The precipitation behavior of B2 particles and the distribution of W in a Ti-47Al-2W-0.5Si alloy were investigated using high-spatial resolution analytical electron microscopy (AEM) and high-resolution electron microscopy (HREM). The ledges at the alpha(2)/gamma interfaces were found to be enriched in W and therefore the preferable nucleation sites for the B2 precipitates. In the B2 phase, as high as one third of Al is substituted by W in comparison with the composition of the 7 phase. The segregation of W to the alpha(2)/gamma and B2/gamma interfaces was also detected. These results provide explanations for the previous observations that additions of tungsten are effective in promoting the creep resistance of TiAl alloys. (C) 2002 Published by Elsevier Science Ltd.