Research on the thermal conductivity and thermal expansion coefficient of TiAl3 ceramics: Influence of Si element and preparation methods

TiAl 3 has emerged as a promising candidate for high-temperature coating applications. In this study, TiAl 3 ceramics (with ∼ 2.3 wt.% Si solid-solved) were prepared via electromagnetic directional crystallization combined with spark plasma sintering (EDC-SPS), using Al alloy scrap (AAS) and Ti sponge as raw materials. First-principles calculations revealed a repulsive interaction between Si and Fe, promoting Fe segregation and removal. Moreover, the heat transfer mode in the TiAl 3 ceramics was a phonon heat transfer. In addition, solid-solved Si reduced the thermal conductivity of EDC-SPS-prepared TiAl 3 ceramics, within the temperature range of 296–823 K, the thermal conductivities were 50-68 W/(m·K) and 30-35 W/(m·K), respectively. Furthermore, compared to TiAl 3 ceramics prepared by pressureless sintering (PS- prepared TiAl 3 ceramics), Si addition stabilized the thermal expansion coefficient (CTE) of EDC-SPS-prepared TiAl 3 ceramics within a low range (11 × 10 -6 K -1 -12 × 10 -6 K -1 ) from 373 K to 823 K. Meanwhile, the EDC-SPS-prepared TiAl 3 ceramics exhibited thermal conductivities comparable to typical high-temperature coating materials and CTEs similar to high-temperature Ti alloys. This study indicates that EDC-SPS-prepared TiAl 3 ceramics using AAS and Ti sponge are promising high-temperature coating materials.