Phase transformations in Cu – Al alloy

The phases obtained in copper aluminum bronze alloy (Cu – 10 wt.% Al – 2 wt.% Fe) cast into a permanent die were investigated. The parameters examined were the preheating temperatures of the die and the graphite coating thickness. The phases α and γ2 were detected as well as the metastable phases β′ and γ′. The intermetallics of the system Fe – Al were obtained in various stoichiometric compositions. The different cooling rates of the casting resulted in two mechanisms of transformation to α grains out of the unstable β phase, one being nucleation and growth producing needle-shaped α grains, the other exhibiting a massive transformation to spherical α grains. These two mechanisms determine the changes in the size of the α grains as a result of changes in the cooling rate in its various ranges.