Investigation on the cracking mechanism of melt growth alumina/aluminum titanate ceramics prepared by laser directed energy deposition

Oxide melt growth ceramics (OMGCs) exhibit excellent performance and microstructure stability near their melting point and are expected to become a new structural material for long-term stable service in extremely high-temperature water-oxygen environments. Owing to its unique advantages of high efficiency, flexible manufacturing, and near-net shaping, laser directed energy deposition (LDED) has become a promising technology for the rapid preparation of high-performance OMGCs. However, owing to the limited understanding of the cracking mechanism, the severe cracking problem that hinders OMGCs-LDED towards engineering applications has not been resolved. Alumina/aluminum titanate (Al₂O₃/Al_xTi_yO_z, A/AT) ceramics are prepared using an LDED system and their cracking characteristics are investigated. Subsequently, numerical simulations are conducted to reveal the dominant factors and influencing mechanisms of the cracking behavior. The results demonstrate that the cracking nucleation process is mainly controlled by solidification defects, whereas the cracking propagation process is determined primarily by both the microstructure and stress level. This study provides a theoretical basis for the development of appropriate cracking suppression methods for OMGCs-LDED.