Burning products of TA15 titanium alloy by friction oxygen concentration method

The microstructural characteristics, elemental distribution law and microscopic formation mechanism of the burning products of TA15 titanium alloy were investigated by friction oxygen concentration method, associated with in situ observation, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses, providing the thoughts to improve fireproof property. The results show that, when the friction contact pressure ( p fric ) is 0.20 MPa and oxygen concentration of premixed air flow ( c 0 ) is 60 vol%, TA15 titanium alloy produces violent sparks and presents dazzling white light during combustion. The generated products after burning are mainly TiO 2 and small amount of Al 2 O 3 oxides. Four distinct zones form from the combustion surface to the alloy matrix, and they are in the sequence of combustion zone, fusion zone, heat-affected zone and transition zone. Further, combustion zone is composed of TiO 2 and Al 2 O 3 compounds, containing obvious cracks. In the fusion zone, discontinuous oxygen-rich Al-based solid solution forms, and the elemental distribution has strong volatility. In the heat-affected zone, there are abundant of Ti-based solid solution and small amount of Al- and Mo-based solid solution. Transition zone is made of lamellar structure. Two technical approaches are given to prevent oxygen diffusion inside the reaction zone and reaction-affected zone. On the one hand, the content of Al is designed as the upper limit of alloy composition; on the other hand, fireproof coatings are deposited on the surface of the alloy.