Strain-hardening during compression of closed-cell Al/Si/SiC + (TiB2 & Mg) foam

• We made three kind Al–Si–SiC–X (X = Mg or X = TiB2) composite foams successfully (experimental, production and tests)
• We developed a simple mathematical model (theoretical) for predicting of strain-hardening of metal foams based on the SEM images and the compression tests and verified it with the experimental tests and results (engineering factors which affect the microstructure–strength relationships of the solid bubbles characterization).
• We introduced 2 models A and B for mechanism of crack propagation in substructures of the solid bubbles wall based on Mg and TiB2 additives (scientific factors which affect the microstructure–strength relationships of materials characterization)
• We revealed “onset-crush point” of cellular structure of the metal foams based on the stress–energy absorption curves for first claim! (mechanical behavior)
• The Mg additive caused that Stress–strain curve of Al–Si–SiC–3% Mg foam show some oscillation during plastic deformation (effect of geometry of solid bubbles on the mechanical behavior of metal foam)

Three sets of Al–Si alloy closed-cell foams, i.e. Al7Si + (3SiC), Al7Si3SiC + (3 Mg), and Al7Si3SiC + (3TiB2) were produced. The deformation behaviors of the foams were then studied by means of compression test. The load–displacement curves showed that foam containing 3 wt.% Mg had considerable stress oscillations. However, the plateau stress and the dissipated energy increased more than 100% for foam with 3 wt.% TiB2. Accordingly, microstructural investigations displayed that compressive responses of foams were dependent on bonding mechanism of SiC and TiB2 particles to the matrix and their distributions. Then, a technique was developed for determination of crushing start point regarding to absorption energy-stress curves. It was found that the hardening for foam with 3 wt.% Mg cannot be described by a simple power-law function, while an asymptotic function is proposed for properly determination of the hardening behavior of foams.

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