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.