Researchers at the University of Leoben (Montanuniversität) in Austria, the country’s university for mining, metallurgy and materials, demonstrated the ability to 3D print the highest strength (1 GPa) alumina through Lithoz‘s recently introduced multi-material approach. Working directly with Lithoz’s engineers, the researchers were able to leverage the layer-by-layer printing process to allow the generation of controlled residual stresses and effectively create a sort of Gorilla alumina. The full paper on this study was just published on Science Direct.
The multi-material approach was employed by embedding alumina-zirconia layers between outer pure alumina layers with significant compressive residual stresses. Because the parts were 3D printed with different materials, the researchers were actually able to digitally control material placement to a degree that these materials became even denser during sintering than alumina alone (monolithic alumina) would.
The 1 GPa measured on the multilayers, compared to 650 MPa in monolithic alumina was achieved through the different material layers compressing even more due to the different temperatures needed for each to sinter: this “thermal mismatch” between material regions during cooling from sintering led to controlled compressive residual stresses.
The combination of layers containing different ceramic materials, connected with strong interfaces, has enabled tailoring alternating in-plane residual tensile and compressive stresses. This approach has been proven by the outstanding results achieved, for example, in “strengthened glasses”, a concept exploited, for instance, in Gorilla glass.
This is the first report of employing additive manufacturing to tailor the strength of alumina ceramics, taking advantage of the layer-by-layer printing process. Designing complex-shaped ceramic architectures with residual stresses through additive manufacturing opens a new path for the fabrication of technical ceramics with tailored mechanical properties.
The outstanding properties of ceramics, such as biocompatibility, resistance to oxidation and corrosion, high-temperature stability, wear resistance as well as special thermal, electrical and optical characteristics, make these materials ideal for demanding technical applications, however fabricating complex geometries using traditional and subtractive ceramics manufacturing methods is extremely costly, using diamond tools, and difficult—if not impossible.
Recent progress in the field of stereolithographic 3D printing techniques such as Lithoz’ Lithography-based Ceramic Manufacturing technology (LCM), has led to major advances in fabricating bulk ceramic materials with mechanical properties comparable to those of ceramics manufactured through traditional routes In recent years, much effort has been directed to designing ceramic based multi-material architectures with improved strength and/or toughness, and in some cases enhanced reliability.