Microstructural evolution during fabrication of alumina via laser stereolithography technique

Application of additive manufacturing (AM) technology in production of ceramic parts is considered as a state-of-the-art technique which has been recently introduced to industry. In the current study the imperative microstructural characteristics of the alumina manufactured via laser stereolithography (SLA) has been investigated. The microstructural characteristics of the developed ceramic parts and components are still unknown and require detailed investigation. A combination of optical microscopy and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), image analysis, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and micro-computed tomography (micro-CT) scans was used to evaluate the microstructural features of the alumina samples after each step of the manufacturing process (i.e. printing, debinding and sintering). In addition, the apparent density of each sample was measured using water displacement method. Results indicated that the porosity of printed alumina samples was significantly reduced after sintering process. EDS analysis confirmed elimination of binder material after debinding and sintering processes. XRD analysis detected existence of α-Al2O3 in initial printed samples which was not changed during debinding and sintering processes. Due to detection of identical peaks for all samples, only one set of lattice parameters (a and c) was calculated from XRD patterns of all samples which was close to the ones reported in literature for alumina. TEM micrographs and corresponding diffraction patterns confirmed polycrystalline structure from different layers of the samples. High resolution transmission electron microscopy (HRTEM) and diffraction patterns from single layers were used to calculate lattice parameters for each sample. A slight increase was noticed in unit cell and grain size after sintering process. The obtained results help for better understanding of the properties through microstructural characteristics of the 3D printed ceramic parts.