THE MICROSTRUCTURE AND INTERFACE BEHAVIOR OF NI/NIAL COMPOSITES PRODUCED BY THE EXPLOSIVE COMPACTION OF POWDERS

Explosive compaction of Ni and NiAl powders was utilized for the processing of Ni/NiAl metal-matrix composites containing up to 57 vol % NiAl particulate. The microstructure, the Vickers microhardness and the Ni/NiAl interfacial bonding strength were studied. The resulting microstructure had a very low volume fraction of porosity (similar to 1 vol %) except for the melting zone formed in the upper portion of a cylindrical specimen. NiAl particles underwent welding during explosive compaction; this was particularly pronounced at the highest volume fractions of NiAl. The lowest microhardness of the Ni matrix was observed in the central portion of a cylindrical specimen. Other parts of the matrix were heavily cold-worked, indicating that a recrystallization had occurred in the centre. NiAl particles were also highly cold-worked regardless of their volume fraction in the composite. The Ni/NiAl interfacial bond strength, measured by the indentation debonding technique, was highest in a composite containing 57 vol % of NiAl particulate.