The structure of bonding between aluminium matrix and ceramic particles in composite materials obtained by hot pressing at the temperature range of 550-640^oC in Degussa press was examined by SEM and TEM methods.
Alumina particles were coated with nickel layer by a chemical method before consolidation with aluminium matrix. The nickel layer observed by SEM consisted of three zones with different grain size of each zone. The zone directly on alumina was continuous and formed of nanograins (10nm and less).
The thermal behaviour of alumina particles coated with nickel and mixture of aluminium powder with alumina particles coated with nickel were examined by differential thermal analysis (DTA) using GDTD 16 analyser produced by SETARAM. The heating rate was set at 13^oC and argon was flowed into processor. The exothermal peak considered with nickel layer and aluminium matrix interaction were noticed at the temperature above aluminium melt point.
After the hot pressing in vacuum of mixture of nickel coated alumina particles and aluminium powder, different structure of ceramic-metal bonding was observed in composite material with the temperature increase. The interface was characterised on polished samples by SEI and X-ray line scans. For the TEM investigation thin foils were prepared for observation in bright field, and microanalysis and electron diffraction were performed.
On the particle-metal border there were three processes noticed considered with nickel diffusion:
a) dissolution of nickel layer in aluminium matrix;
b) transformation of nickel layer into a nickel aluminides layer;
c) formation of single particles from Al-Fe-Ni system.
The presence of particles from Al-Fe-Ni system on the interface can be explained as a result of iron impurity in aluminium powder of 99.7 % purity.

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