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 alpha and gamma(2) were detected as well as the metastable phases beta' and gamma'. 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 alpha grains out of the unstable beta phase, one being nucleation and growth producing needle-shaped alpha grains, the other exhibiting a massive transformation to spherical alpha grains. These two mechanisms determine the changes in the size of the alpha grains as a result of changes in the cooling rate in its various ranges.