In recent years an entirely new and novel system of rapid manufacturing of aluminium matrix composites by an infiltration and reaction has been under development. This involves the growth of an AlN skeleton through an AA6061 powder part and the subsequent infiltration with liquid AA6061. It is currently believed that the covalent surface of AlN facilities wetting and thus infiltration.
This thesis reports the effect inclusion of AlN and Al2O3 powder has on infiltration. Preform were made composed of AA6061-3wt%Mg-1wt%Sn-5%Nylon with 10wt%, 20wt%, 40wt% and 70% AlN or Al2O3. The Sn is used to control the rate of skeleton growth, the Mg is an oxygen scavenger to allow the formation of AlN instead of Al2O3, and the Nylon is to bind the part prior to skeleton growth. Parts were also made consisting of AlN-3wt%Nylon and AlN-2wt%-Mg-3wt%Nylon.
The nitridation was performed at 560ºC for 12hrs and infiltration was performed at 700ºC over 2hrs. This was completed in a single thermal cycle.
Full infiltration was achieved in samples contain 10wt%AlN, 20wt%AlN, 10wt%Al2O3, 20wt%Al2O3, 40wt%Al2O3. Partial infiltration was achieved in the sample containing 40wt%AlN. No infiltration was achieved in the 70%AlN, 70wt%Al2O3, AlN-3wt%Nylon and AlN-2wt%Mg-3wt%Nylon. This suggests that AlN is not being wet by liquid AA6061.
Analysis of the microstructure showed dissimilarity between the AlN particles and the skeleton. This and the failure of AlN to infiltrate indicates that the skeleton may not be AlN.