Synthesis of an Al/MgAl2O4In situ Metal Matrix Composite from Silica Gel |
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Authors: | V M Sreekumar R M Pillai B C Pai M Chakraborty |
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Affiliation: | Regional Research Laboratory (CSIR), Thiruvananthapuram-695019, India; Indian Institute of Technology, Kharagpur 721302, India |
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Abstract: | An aluminum/MgAl2O4 in situ metal matrix composite has been synthesized using silica gel containing ∼98% SiO2 in an Al–5Mg alloy. The thermodynamics and kinetics of MgAl2O4 formation have been discussed in detail. A transition phase of composition between MgO and MgAl2O4 has been detected in the SEM-EDS analysis of the particles extracted from the composite by a 25% NaOH solution. This confirms the gradual transformation of MgO to MgAl2O4 by the reaction 3SiO2( s )+2MgO( s )+4Al( l )→2MgAl2O4( s )+3Si( l ). The stoichiometry, n , of MgAl2O4 has been found to sustain close to 1 and the crystallite growth of MgAl2O4 has been stopped at D ∼30 nm in the composites held at 750°C up to 10 h. |
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