title: Microstructural development in Al/MgAl2O4in situmetal matrix composite using value-added silica sources.
abstract: Al/MgAl2O4in situmetal matrix composites have been synthesized using value-added silica sources (microsilica and rice husk ash) containing ∼97% SiO2in Al-5 wt.% Mg alloy. The thermodynamics and kinetics of MgAl2O4formation are discussed in detail. The MgO and MgAl2O4phases were found to dominate in microsilica (MS) and rice husk ash (RHA) value-added composites, respectively, during the initial stage of holding the composites at 750 °C. A transition phase between MgO and MgAl2O4was detected by the scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) analysis of the particles extracted from the composite using 25% NaOH solution. This confirms that MgO is gradually transformed to MgAl2O4by the reaction 3SiO2(s)+2MgO(s)+4Al(l)→2MgAl2O4(s)+3Si(l). The stoichiometry of MgAl2O4,n, computed by a new methodology is between 0.79 and 1.18. The reaction between the silica sources and the molten metal stopped after 55% of the silica source was consumed. A gradual increase in mean MgAl2O4crystallite size,D, from 24 to 36 nm was observed in the samples held for 10 h.
authors.affiliation: National Institute for Interdisciplinary Science and Technology (CSIR), Thiruvananthapuram - 695019, India.
authors.forename: Vadakke
authors.initials: V
authors.lastname: Madathil Sreekumar
authors.affiliation: National Institute for Interdisciplinary Science and Technology (CSIR), Thiruvananthapuram - 695019, India.
authors.forename: Raman
authors.initials: R
authors.lastname: Marimuthu Pillai
authors.affiliation: National Institute for Interdisciplinary Science and Technology (CSIR), Thiruvananthapuram - 695019, India.
authors.forename: Bellampettu
authors.initials: B
authors.lastname: Chandrasekhara Pai
authors.affiliation: Indian Institute of Technology, Kharagpur - 721302, India.
authors.forename: Madhusudhan
authors.initials: M
authors.lastname: Chakraborty
keywords: MgAl2O4; configurational entropy; reactive wetting; stoichiometry