Fabrication and mechanical properties of Al/Al2O3 composite bodies by reactive infiltration of molten Al into SiO2 preform

Al/Al2O3 composites were fabricated by a displacement reaction between SiO2 and molten Al. In this study, fabrication of Al/Al2O3 composites was attem pted by means of reactive infiltration to provide variation of their mechan ical properties. SiO2 preforms having various porosities and pore size dist ributions were prepared by sintering the powder at different temperatures b etween 1273 and 1723 K, Molten Al was infiltrated at 1373 K without applica tion of pressure, Infiltration kinetics were studied and the microstructure s of the composite bodies were observed by means of scanning electron micro scopy (with energy dispersive x-ray microanalysis), wave dispersive x-ray m icroanalysis, and x-ray diffractions. The infiltrated specimens were mainly composed of Al and alpha -Al2O3 phases, and the Si content was less than 5 at.%. Volume fraction of Al phase in the composite bodies was not altered very much with the porosities of the SiO2 preforms because of the difficult y in filling out the entire pore space. Properties and microstructures of A l/Al2O3 composites, however, were dependent on the sintering temperature of the SiO2 preforms, In the case of low sintering temperature, a thick Al ch annel existed, which deformed upon compression. In the case of high sinteri ng temperature, the microstructure became homogeneous and had thinner Al ch annels. The composite bodies became brittle. The deformation behavior was s hown to be changed from ductile to brittle as an increase of the sintering temperature of the preforms.