Control of sintering kinetics and thermal shock resistance for stereolithography 3D printed ceramics

Stereolithography has had a transformative impact on the production of complex Al₂O₃ ceramic components. However, the high melting point and inherent brittleness of Al₂O₃ ceramics limit its application in the aerospace field. In this research, we investigated the influence on the microstructure, physical properties, mechanical properties, and thermal shock resistance (TSR) properties of the addition of TiO₂-doped Al₂O₃ ceramics by stereolithography 3D printing technology. This work revealed the relationship between the addition of TiO₂ and the sintering kinetics of Al₂O₃ ceramics. TiO₂ forms Al₂TiO₅ with Al₂O₃ at high temperatures, which promoted the growth of ceramic grains, increased the bulk density, reduced the porosity, and improved the flexural properties of Al₂O₃ ceramics. During the cooling step of the sintering process, the anisotropy of thermal expansion coefficients of Al₂TiO₅ and the difference in thermal expansion coefficients between the different phases (Al₂O₃ and Al₂TiO₅) generate thermal stresses which ultimately cause microcracks in the low strength Al₂TiO₅. The presence of microcracks within the Al₂TiO₅ causes thermal cracks to deflect during expansion, which passivated the crack tip effect. And TiO₂ promoted Al₂O₃ sintering to raise the critical value of crack tip stress. Both mechanisms can improve the residual flexural strength of Al₂O₃ ceramics, thereby improving TSR. Overall, the critical flexural strength of 2 wt% TiO₂/Al₂O₃ was the highest, reaching 165.158 MPa, and the corresponding critical thermal shock temperature difference was 264.10 °C. Based on the above study, samples with high TSR had been successfully produced using stereolithography 3D printing technology, which will promote the application of Al₂O₃ ceramics in the aerospace field.