Strength and fracture of two hot-rolled Ti-Al-Si-Nb dual phase alloys based on Ti3Al

Ti-Al-Si-Nb dual phase alloys are mainly composed of alpha(2)-Ti3Al matrix and Ti5Si3 silicide phases. In this paper, two alloys (402 and 405) whose S i contents are 2 and 5 at% respectively were are melted and hot-rolled into sheets with different amounts of deformation. The silicide phase (Ti,Nb)(5 )(Si,Al)(3) was broken up into small pieces and redistributed in the alpha( 2) matrix during the hot-rolling. improved strength and ductility of the tw o alloys were observed after hot-rolling, which can be attributed to both t he finely distributed reinforcement silicide phase and refinement of the ma trix grain size. The mechanical properties of the two alloys are dependent on their volume fractions of the silicide phase: the strength of alloy 405 is higher than that of alloy 402, while alloy 402 is more ductile than allo y 405. The brittle-ductile transition temperature of the two dual phase all oys is between 600 and 800 degrees C. The surface slip on the dual phase al loys was also observed. Obvious separation between the (Ti,Nb)(5)(Si,Al)(3) particles and the alpha(2) matrix is found on the fracture surfaces obtain ed at high temperature, showing dimple-like morphology. (C) 2000 Elsevier S cience Ltd. All rights reserved.