Melt-grown behaviour of heat treated high-purity alumina ceramics prepared by laser directed energy deposition

Laser additive manufacturing technologies have attracted attention for the rapid preparation of melt-grown oxide ceramics, which are promising for high-temperature applications. However, the limitation of the mechanical properties and lack of understanding of high-temperature stability limit the applications of this type of material. In this study, the effect of heat treatment on melt-grown high-purity alumina ceramics prepared by laser-directed energy deposition (LDED) was investigated. The results show that melt-grown alumina ceramics have excellent high-temperature stability, as evidenced by the negligible changes in weight, geometric size, roughness, and phase composition after heat treatment. Compared with the same deposited material without heat treatment, the flexural strength of the heat-treated material is significantly increased, and the maximum strength can reach 547.85 +/- 78.81 MPa, an increase of 102.96%. This increase in strength is attributed to crack healing during the heat treatment process. The heat treatment had less influence on the microhardness and fracture toughness. The results presented here can provide technical guidance for the fabrication of high-performance melt-grown high-purity oxide ceramics using LDED technology.