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Metal matrix syntactic foams are consisting of metal matrix and hollow spheres in closely or randomly packed, which own multifunctional properties with lightweight, damping, heat insulation, energy absorption and have a vast application prospect. Steel matrix can extend the potential of syntactic foams as a materials class to several new fields of application. In this paper, the hollow alumina spheres were introduced into the steel matrix by infiltration casting, the minimum diameter of hollow spheres for infiltration is analyzed in theory, the steel matrix syntactic foams were successfully prepared, which contain two different sphere types with average diameter sizes 3.97mm and 4.72mm, and the average densities of syntactic foams were calculated to be 4.39 (spheres occupy 43.7% of the volume) and 3.74 g/cm3 (spheres occupy 52.1% of the volume), respectively. The microstructure characteristics of the steel matrix syntactic foam were analyzed by means of scanning electron microscopy and energy spectrum.

As a new type composite material, steel-based porous materials presented the higher stiffness, strength and higher temperature resistance in comparison with the nonferrous metals. In order to realize the free-design of pore structure and free-control of porosity of steel-based porous material, indirect 3D printing technology combined with the investment casting process has been used to fabricate the steel-based porous materials. The finite element method has been carried out to study the relationship between the porosity and the mechanical properties by quasi-static compression simulation, which is consistent with compression test. The modified Gibson-Ashby formula is used to establish the quantitative relationship between porosity and elastic modulus and yield strength of steel-based porous materials based on Kelvin structure.