In-situ preparation and mechanical properties of gradient porous metal composite structures

The designability of gradient porous materials facilitates the realization of multi-stage energy absorption protection, yet the interlayer interface bonding needs to be improved. This study innovatively employed the infiltration casting technology to fabricate the gradient porous metal composite structures composed of aluminum foam, aluminum matrix syntactic foam and aluminum alloy solid, with significant property differences. The microstructure characterization confirmed that a metallurgical bond was formed between the foams and solid layer, but there were still interface gaps. Combining quasi-static compression and μ-CT, these structures exhibited a multi-stage stress plateau and a mechanism of sequential failure from low-strength porous layers to high-strength porous layers, with no fracture occurring at the interface. The three-dimensional confinement effect caused by interlayer cooperative deformation significantly enhanced the equivalent yield strength of the porous layer. At strain 0.3, the gradient structure with two layers of syntactic foam and one layer of aluminum foam can improve the energy absorption and specific energy absorption by up to 6.5 and 7.0 times respectively compared with the gradient structure with one layer of syntactic foam and two layers of aluminum foam. This transformation mode from soft start to hard support offers significant application potential in various scenarios of impact protection.