Microstructure and macro properties of Al2O3 ceramics prepared by laser engineered net shaping

Laser engineered net shaping (LENS) technology, due to its ability in melting and solidification of neat ceramic materials, exhibits great potential for direct fabricating net-shaped ceramic structures. However, due to limitation of sample size, reports on the macro properties of fabricated ceramic structures are still extremely lacking. In the present work, large-sized Al2O3 ceramic samples were prepared using LENS technology to perform microstructural analysis and macro properties testing. Phase composition, grain characteristics and chemical purity of prepared samples were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray fluorescence (XRF). Macro properties of large-sized samples, including the flexural strength and compressive strength, were given for the first time after being tested using a mechanical tester. Results show that microstructure of prepared Al2O3 ceramics presents typical solidification characteristics and consists of grains that grow along the deposition height direction. Primary dendrite spacing of the Al2O3 grains is about 60 mu m. The phase is mainly composed of high-temperature-stable alpha-Al2O3 and a relative density of 99.5% is obtained. No new impurities are introduced during the depositing process. Element type and element content of fabricated samples are highly consistent with those of original powder. Property test results show that, under current process conditions, the flexural strength and compressive strength of fabricated samples reaches the level of traditional sintering method, reaching the maximum of 350 MPa and 625 MPa respectively.