Novelty phase synthesis mechanism and morphology in resin-bonded Al–Al2O3–TiO2 composites at high temperatures under flowing N2

An Al–AlN core–shell structure is beneficial to the performance of Al–Al2O3 composites. In this paper, the phase evolution and microstructure of Al–Al2O3–TiO2 composites at high temperatures in flowing N2 were investigated after the Al–AlN core–shell structure was created at 853 K for 8 h. The results show that TiO2 can convert Al into Al3Ti(~1685 K), which reduces the content of metal Al and rearranges the structure of the composite. Under N2 conditions, Al3Ti is further transformed into a novelty non-oxide phase, TiCN. The transformation process can be expressed as follows: Al3Ti reacts with C and other carbides(Al4C3 and Al4O4C) to form TiCx(x < 1). As the firing temperature increases, Al3Ti transforms into a liquid phase and produces Ti(g) and TiO(g). Finally, Ti(g) and TiO(g) are nitrided and solid-dissolved into the TiCx crystals to form a TiCN solid solution.