Strain-rate-dependent behavior of additively manufactured alumina ceramics: Characterization and mechanical testing

Abstract

This study experimentally investigates the mechanical behavior of additively manufactured (AM) alumina ceramics by stereolithography technique. The AM alumina specimens with two different printing orientations (POs) are tested under quasi-static and dynamic loading rates. The material shows a quasi-static (i.e., a strain rate of 10−3 s−1) compressive strength of 1640.54 ± 99.33 MPa and 1494.25 ± 260.08 MPa for the PO1 and PO2, respectively, and a dynamic (i.e., a strain rate of 640–730 s−1) compressive strength of 3077.25 ± 174.07 MPa and 3107.33 ± 97.03 MPa for the PO1 and PO2, respectively, which are among the highest reported values for AM alumina due to the higher density and finer grain size. The strain-rate-dependent compressive strength of the material is slightly affected by the PO which is alleviated with the increase in strain rate from quasi-static to dynamic loading conditions. In contrast, the PO noticeably affects the macro-scale failure pattern. The fractography analysis shows the dominant contribution of the intergranular failure mechanism and a combination of intergranular and transgranular mechanisms under quasi-static and dynamic loading, respectively. The crack speed propagation is found to be 785 ± 174 m/s on average which is ∼68% less than that of conventional ones in the literature. The current AM alumina shows a hardness of 24.45 ± 0.88 GPa which is higher than that of the majority of other AM alumina. Overall, this study discusses the potentiality of using AM ceramics in engineering fields replacing the conventionally-made counterparts, and provides implications for designing better-performing AM ceramics.

Keywords

• Additive manufacturing (AM)
• Alumina (Al2O3) ceramic
• Failure mechanisms
• Printing orientation (PO)
• Strain-rate-dependent mechanical behavior