Study of the thermal stability of the Al4SiC4 phase via experiments and thermodynamic assessment

Abstract

The Al4SiC4 phase is a potential new refractory material due to its high compressive strength at high temperatures. However, the thermal stability of the Al4SiC4 phase is not clear. The thermal stability of the Al4SiC4 phase has been studied. The Al-Si-C samples were prepared using the powder metallurgy method and were sintered/annealed at 1500 °C, 1400 °C, 1300 °C, 1200 °C and 500 °C, followed by XRD, SEM, and EPMA testing. It was found that the Al4SiC4 phase is unstable below 1400 °C and stable above 1500 °C. The isothermal sections of the Al-Si-C system at 1500 °C, 1200 °C and 500 °C were experimentally obtained. The Al4SiC4 phase was synthesized at 1650 °C. It was found that with the addition of the Al4SiC4, the strengths of the SiC-2xxx composite were not increased. It is because the Al4SiC4 reacted with the Al2Cu phase. The thermodynamic description of the Si-C-Al system was carried out using the CALPHAD method. The CALPHAD simulated results are consistent with the present experimental studies. The results show that the stabilization temperature of the Al4SiC4 phase ranges from 1463 °C to 2088 °C.