Microstructure evolution and mechanical properties of Al_(2)O_(3)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 Al_(2)O_(3) 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 Al_(2)O_(3) 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 Al_(2)O_(3) content.The expansion from Al_(2)O_(3) outward growth and Al granule precipitation counteracts the shrinkage from E12 decomposition and Al_(2)O_(3) 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.Ourfindings reveal the relationship between microstructure evolution and property optimization of high-performance ceramic foams,with potential significance for microstructure design and practical application.