Abstract: SiC-MgAl₂O₄ composites were fabricated in flowing nitrogen for 5 h at 1 500 ℃, using SiC and MgAl₂O₄ powders as well as various mass fraction of 1%, 3%, 5%, 7%, 9% and 12% aluminum powders as the raw materials. The sintered samples were analyzed by XRD, SEM and EDS. The results show that a series of reactions occur in the material system after sintering at 1 500 ℃. β-SiC, MgAl₂O₄, nitride and sialon as the main phases are detected in all the sintered samples. Aluminum is partially nitridated at high temperature to form aluminum nitride and participate in the reaction of sialon and MgAlON formation. The spinel is transformed into two phases coexisting with aluminum-rich spinel and MgAlON. With the increase of aluminum content, α-Al₂O₃ can be precipitated when the solid-solute aluminum in spinel reaches to the content limit. Moreover, as the aluminum content increases, the morphology of the Si-Al-O-N phase changes from slab-band shape to slab-columnar shape, and eventually develops a clearer plate layer shape. A certain amount of Mg element is dissolved in the sialon phase by SEM-EDS analysis, which is considered as the sialon polymorph of Mg-sialon phase.

Key words: refractory, aluminum powder, nitrogen atmosphere, SiC-MgAl₂O₄ composite, microstructure, phase composition