Microstructure evolution and oxidation behaviour of Ti<inf>f</inf>/TiAl<inf>3</inf> composites: Fid-Bau Portal

Microstructure evolution and oxidation behaviour of Tif/TiAl3 composites

Yang, W.S. / Xiu, Z.Y. / Wang, X. / Liu, Y.M. / Chen, G.Q. / Wu, G.H.

Abstract In this paper, Tif/TiAl3 composites were fabricated by infiltration–in situ reaction method and its oxidation behaviours were investigated by cyclic oxidation testing at 700°C, 800°C and 900°C. The microstructure evolution and oxidation of Tif/TiAl3 composites were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray diffraction (EDX). The reaction between Ti3Al particles and Al was more violent than that of Ti fibres and Al. Ti3Al/Al reaction consumed a large amount of Al and inhibited the reaction of Ti fibres indirectly. Reactant of Ti fibres was TiAl3 at 700°C, and four reaction layers surrounding Ti fibre (Ti3Al, TiAl, TiAl2 and TiAl3 from inner to outside) were observed above 800°C. The thickness of the total reaction layers increased little with temperature and time, while the thickness of inner reaction layers increased remarkably. A model corresponding to the microstructure evolution process was drawn schematically. Oxidation resistance of Tif/TiAl3 composites decreased with increasing of temperature, and changed from cubic law at 700°C to parabolic law at 900°C. The oxidation weight gain of Tif/TiAl3 composite was dominated by the exposed Ti fibres. Due to outward diffusion of Ti and Al element, the oxide of Ti fibre at 900°C changed to mushroom-shape. Fortunately, when TiAl3 was oxidized, a thin and continuous Al2O3 layer was formed, protecting matrix from further oxidation.