Oxidation behavior and effect of oxidation on microstructure and tensile properties of Ti–5Al–5Mo–5V–1Cr–1Fe alloy

Abstract

Abstract In this study, both oxidation behavior and tensile properties of Ti–5Al–5Mo–5V–1Cr–1Fe alloy are investigated in air between 100 °C and 1000 °C. X-ray diffraction and light optical microscope are used to characterize the phase composition and morphology of oxide layers, respectively. The mixed oxide layer consists of the white TiO 2 , the golden TiO and blue Ti 2 O 3 , with white TiO 2 being the dominant oxide phase. These colored titanium oxides result in different colors on the surface of the specimens. The oxidation has a significant effect on the tensile properties of the alloy. Both adherent oxide layer and stable microstructure of adequate equiaxed α phase within a fine β transformed matrix are primarily responsible for a good combination of strength and ductility below 750 °C. However, as the alloy oxidized above 750 °C, both strength and ductility decrease dramatically due to the formation of defective oxide layer and coarsed β grains. An reliable oxidation model is proposed to predict the thickness of the oxide layer after taking the spalled oxide layer thickness into account. Moreover, the spallation of oxide layer leads to a fracture mode change from ductile fracture in specimens with dense oxide layer to a mixture of ductile fracture and brittle intercrystalline fracture in specimens with defective oxide layer.