Characterization of aluminized layer formation during annealing of Ti coated with an Al film

During annealing of the Ti surface coated by the Al film, different aluminide phases were formed as the result of reactions between Ti and Al. The structural formation of aluminide phases and the microstructure formed after annealing treatment depended on the thickness of the initial Al film. After annealing treatment up to 900 °C, the microstructure of the overlayer clearly showed contours of grain boundaries of the initial Ti substrate. The shapes, sizes and distribution of the particles in the overlayer depended on the microstructure of the initial Ti substrate as well. The microstructure of the initial Ti substrate had a great effect on the transformation kinetics. Retardation of the reaction was observed on the substrate with lamellar structure. After the elimination of the overlayer, a fine plate structure was formed. The change of the phase compositions of the overlayer led to change in the microhardness. The peak value of the microhardness was observed with the lamellar like morphology of overlayer.