Development of Si 3N 4/Al composite by pressureless melt infiltration

Abstract

Pressureless infiltration processs to synthesize Si 3N 4/Al composite was investigated. Al-2%Mg alloy was infiltrated into Si 3N 4 and Si 3N 4 containing 10% Al 2O 3 preforms in the atmosphere of nitrogen. It is possible to infiltrate Al-2% Mg alloy in Si 3N 4 and Si 3N 4 containing 10% Al 2O 3 preforms. The growth of the dense composite of useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. During infiltration Si 3N 4 reacted with aluminium to form Si and AlN, the growth of composite was found to proceed in two ways, depending on the Al 2O 3 content in the initial preform. Firstly, preform without Al 2O 3 content gives rise to AlN, Al 3.27Si 0.47 and Al type phases after infiltration. Secondly, perform with 10% Al 2O 3 content gives rise to AlN-Al 2O 3 solid solution phase (AlON), MgAl 2O 4, Al and Si type phases. AlON phase was only present in composite, containing 10% Al 2O 3 in the Si 3N 4 preforms before infiltration.