Strength and fracture of two hot-rolled Ti–Al–Si–Nb dual phase alloys based on Ti 3Al

Abstract

Ti–Al–Si–Nb dual phase alloys are mainly composed of α 2-Ti 3Al matrix and Ti 5Si 3 silicide phases. In this paper, two alloys (402 and 405) whose Si contents are 2 and 5 at% respectively were arc 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 α 2 matrix during the hot-rolling. Improved strength and ductility of the two alloys were observed after hot-rolling, which can be attributed to both the finely distributed reinforcement silicide phase and refinement of the matrix 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 alloy 405. The brittle–ductile transition temperature of the two dual phase alloys is between 600 and 800°C. The surface slip on the dual phase alloys was also observed. Obvious separation between the (Ti,Nb) 5(Si,Al) 3 particles and the α 2 matrix is found on the fracture surfaces obtained at high temperature, showing dimple-like morphology.