Abstract

Lightweight materials with improved strength characteristics are increasingly required in aerospace, automotive, impact protection, and vibration damping applications to enhance structural efficiency and service life. Although aluminum metal foams have been found to be promising lightweight cellular materials, their load-bearing performance is rather limited, thus limiting their use for high-performance structural applications. The composite metal foams in the present study were produced by CaCO3 as foaming agent and AA7075 as the base material by gas-releasing particle decomposition method, in which the foaming agent is transformed into CO2 gas to generate pores during foaming. Cell size distribution analysis, density, and energy-dispersive spectroscopy were used to investigate the composite foams containing 0, 1, 2 and 3 wt.% Si3N4, while quasi-static uniaxial compression testing was employed to measure the compressive strength of these foams. Si3N4 of 2 wt.% and 3 wt.% resulted in better pore refinement and uniformity of cells, as revealed in the microstructural analysis. The density was raised from 0.21 to 0.61 g/cm3 by reinforcement addition. The compression strength increased from 7.85 to 23.64 MPa, while energy absorption increased from 5.10 to 20.52 MJ/m3 for foams containing 0 and 3 wt.% Si3N4, respectively. The yield strength also improved from 4.92 to 15.98 MPa, and the plateau stress from 7.37 to 22.57 MPa. Improved mechanical behavior is due to the following: refinement of pores, thickness of the ligaments, more compact structure, and load transfer in the cellular structure.

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