Formation mechanisms of Ti₃(Si,Al)C₂/Al₂O₃ composites from Ti₃AlC₂ and SiO via low-temperature sintering

Ti₃SiC₂/Al₂O₃ composites have attracted attention due to their excellent mechanical and electromagnetic properties, but the high temperatures (≥ 1400 ℃) required for the densification of aluminum oxide (Al₂O₃) leads to the decomposition of Ti₃SiC₂. To address this issue, Ti₃(Si_xAl_1−x)C₂/Al₂O₃ (x represents the Si content) composites were synthesized for the first time via hot-pressing (HP) sintering and current-assisted sintering (CAS) of mixed Ti₃AlC₂ and silicon monoxide (SiO) powders at 1300 and 1200 ℃, respectively. Both approaches produced composites with x values greater than 0.9, indicating that the compositions of the prepared composites were similar to those of Ti₃SiC₂/Al₂O₃ composites. The synthetic mechanism involved substitution and continuous interdiffusion of Al and Si atoms. The composite prepared by CAS at 1200 ℃ was compacted, whereas the composite prepared by HP had a low density. The low-temperature densification mechanism is attributed to the combined effects of amorphous SiO, liquid Al, and the high heating rates for CAS. The flexural strength and hardness of the composite prepared by CAS were also comparable to those of compacted Ti₃SiC₂/Al₂O₃ composites.