Microstructure evolution and mechanical properties of Al2O3 foams via laser powder bed fusion from Al particles

Laser powder bed fusion (LPBF) combined with reaction bonding (RB) of Al particles is an effective method for preparing high-performance 3D Al₂O₃ ceramic foams. However, the indistinct microstructure evolution hinders the regulation of pore features and the improvement of synthetic properties. Herein, the microstructure evolution of the Al₂O₃ ceramic foams during the LPBF/RB process is clarified by various characterization methods, and the corresponding mechanical property modulation is realized by optimizing LPBF parameters, organic binder (E12 epoxy resin) content, heating rate, sintering time, and coral-like Al₂O₃ content. The expansion from Al₂O₃ outward growth and Al granule precipitation counteracts the shrinkage from E12 decomposition and Al₂O₃ sintering, resulting in an ultra-low shrinkage of 0.94%–3.01%. The pore structures of particle packing pores, hollow spheres, and microporous structures allow a tunable porosity of 52.6%–73.7%. The in-situ formation of multi-scale features including hollow spheres, flaky grains, whiskers, nanofibers, and bond bridges brings about a remarkably high bending strength of 6.5–38.3 ​MPa. Our findings reveal the relationship between microstructure evolution and property optimization of high-performance ceramic foams, with potential significance for microstructure design and practical application.