Flexural strength of a conventionally processed and additively manufactured debased 94% alumina

• Published in: International journal of applied ceramic technology Vol. 19; no. 3
• Main Authors: Kammler, Daniel R., Cillessen, Dale E., Ford, Kurtis R., Larkin, Elizabeth C., Davidson, Will M., Christopher, James M., Gibson, Julie T.
• Format: Journal Article
• Language: English
• Published: United States Wiley 23.11.2021
• Subjects: additive manufacturing; alumina; fracture mechanics/toughness; glass-ceramics; lithography; MATERIALS SCIENCE
• ISSN: 1546-542X; 1744-7402

Mechanical strength of a 94 wt% debased alumina was measured using ASTM-C1161 specimens fabricated via conventional and lithography-based ceramic manufacturing (LCM) methods. The effects of build orientation and a 1500°C wet hydrogen fire added to the LCM firing sequence on strength were evaluated. Additionally, a Weibull fit to the conventional flexural specimen data yielded 20 and 356 MPa for the modulus and characteristic strength, respectively. Weibull fits of the data from the LCM specimens yielded moduli between 7.5 and 11.3 and characteristics strengths between 333 and 339 MPa. A Weibull fit to data from LCM specimens subjected to the wet hydrogen fire yielded 14.2 and 376 MPa for the modulus and characteristic strength, respectively. The 95% confidence intervals for all Weibull parameters are reported. Average Archimedes bulk densities of LCM and conventional specimens were 3.732 and 3.730 g/cm3, respectively. Process dependent differences in surface morphology were observed in scanning electron microscope (SEM) images of specimen surfaces. SEM images of LCM specimen cross-sections showed alumina grain texture dependent on build direction, but no evidence of porosity concentrated in planes between printed layers. Fracture surfaces of LCM and conventionally processed specimens revealed hackle lines and mirror regions indicative of fracture initiation at the sample surface rather than the interior.