Synthesis and Analysis of Nanocrystalline β1-Cu3Al and β2-NiAl Intermetallic-Reinforced Aluminum Matrix Composite by High Energy Ball Milling

Nanocrystalline beta(1)-Cu3Al and beta(2)-NiAl intermetallic compounds were in-situ reinforced in the aluminum matrix with the atomic composition of Al67Cu20Ni13 by the mechanical alloying of elemental powders. Both beta(1)-Cu3Al, beta(2)-NiAl phases that can be only co-synthesized in Cu base alloys have been obtained after 15h milling in this study. The phase evolution during milling process was investigated by X-ray diffraction. The beta(1)-Cu3Al, beta(2)-NiAl phases were metastable with further milling time up to 40 h. Specially, unreacted Al matrix has been totally transformed to amorphous state in the final powder. A remarkable crystalline size of 6.5 nm was reached after 15 h milling time. Thermal stability of the milled powder was also studied by differential thermal analysis. It is shown that beta(1)-Cu3Al, beta(2)-NiAl phases were stable up to higher than 550 degrees C. Moreover, the inter-diffusion between Al matrix and Cu(3)A(1) within the temperature range of 620-740 degrees C led to the formation of superstructure zeta(1)-Al3Cu4 phase.