Direct additive manufacturing of large-sized crack-free alumina/aluminum titanate composite ceramics by directed laser deposition

Abstract

Purpose Direct additive manufacturing of ceramics (DAMC) is a highly promising ceramics preparation technology because of its simple process and rapid response capability, but the cracking issue prevents its industrial application. The purpose of this paper is to propose aluminum titanate (Al2TiO5) with low coefficient of thermal expansion (CTE) to suppress cracks during the DAMC. Design/methodology/approach Al2O3/Al2TiO5 (A/AT) composite ceramic samples with different compositions were in-situ synthesized from Al2O3/TiO2 (A/T) powder in a directed laser deposition (DLD) process. The relationship between the content of TiO2 and cracking characteristics of fabricated sample was discussed. Phase composition, microstructure and properties of the fabricated samples were also investigated. Findings The results of this paper show that the doping of TiO2 can obtain Al2TiO5 synthesized in situ by reaction with Al2O3 and effectively suppress cracks during DAMC. When the content of TiO2 reaches 30 wt.per cent, cracks hardly occur even under conditions of slow deposition. Crack-free structures such as vane, cone and pyramid were successfully prepared, with a maximum cross-sectional dimension of 30 mm and maximum length of 150 mm. A continuous matrix phase formed of the low CTE of Al2TiO5 is the major cause of crack suppression. The dispersed distribution of a-Al2O3 columnar dendrites has the effect of increasing the strength of the matrix. Under current process conditions, the prepared sample with 10 wt.per cent TiO2 has micro-hardness of 21.05 GPa and flexural strength of 170 MPa. Originality/value This paper provides a new method and inspiration for direct additive manufacturing of large-sized crack-free ceramics, which has the potential to promote practical application of the technology.