Reactive hot compaction of functionally graded composites

Reactive Bot compaction (RHC) of Ni and Al powder mixtures, in which one or both of the powders were partially oxidized, has been carried out to fabricate NiAl-in situ-alumina composites. The alumina was found to reach values of 52 vol%. Microhardness values were found to increase by increasing the alumina content. No cracks were seen around the Vickers indentations, suggesting toughening of NiAl by the in-situ alumina. The heating rate during the RHC process as well as the sample volume were found to be interrelated with the volume fraction of porosity. Larger sample volumes resulted in higher amounts of porosity because of relatively Larger temperature build up in the sample. The application of RHC to form NiAl/Alumina FGM consisting of five layers has also been investigated.