Redox-reaction phenomenon in cenosphere reinforced aluminum alloy matrix syntactic foam

Abstract To investigate the effect of interfacial diffusion during solidification on the dispersion of light hollow particles, the cenosphere-reinforced aluminum-magnesium (Al-Mg) alloy matrix syntactic foams (MSF) were synthesized by stir casting. Microstructures of the foams were characterized by computed tomography, energy dispersive spectrometry, and electron backscatter diffraction. Cenosphere shells containing Al2O3 and SiO2 were decomposed by redox-reaction, and MgAl2O4 was formed on the shell by interfacial diffusion during solidification. This phase transformation was effective in forming Al-Mg alloy MSF with a high volume of cenosphere, which increased by about 50%. Magnesium silicide (Mg2Si) precipitates were also formed on the matrix by SiO2 reduction.