Interface study by dual-beam FIB-TEM in a pressureless infiltrated Al(Mg)–Al2O3 interpenetrating composite
journal contributionposted on 06.02.2009, 10:28 by H. Chan, Rebecca Higginson, J.G.P. Binner
This paper considers the microstructures of an Al(Mg)/Al2O3 interpenetrating composite produced by a pressureless infiltration technique. It is well known that the governing principle in pressureless infiltration in Al/Al2O3 system is the wettability between the molten metal and the ceramic phase; however, the infiltration mechanism is still not well understood. The objective of this research was to observe the metal / ceramic interface to understand the infiltration mechanism better. The composite was produced using an Al-8wt.% Mg alloy and 15% dense alumina foams at 915°C in a flowing N2 atmosphere. After infiltration, the composite was characterized by a series of techniques. Thin film samples, specifically produced across the Al(Mg)-Al2O3 interface, were prepared using a Dual Beam Focused Ion Beam (FIB) and subsequently observed using Transmission Electron Microscopy (TEM). XRD scan analysis shows that Mg3N2 formed in the foam at the molten alloy-ceramic infiltration front whilst TEM analysis revealed that fine AlN grains formed at the metal / ceramic interface and MgAl2O4 and MgSi2 grains formed at specific points. It is concluded that it is the reactions between the Al, Mg and N2 atmosphere that improve the wettability between molten Al and Al2O3 and induce spontaneous infiltration.
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