Influence of mould parameters on the microstructure of cast copper aluminium bronze

The phases obtained in copper aluminium bronze alloy (Cu-10wt.% Al-2wt.% Fe) cast into a permanent mould were investigated. The parameters examined were the thickness of the graphite coating of the mould and its pre-heated temperature. The phases a and gamma(2) were detected as well as the metastable phases beta' and gamma'. The intermetallics of the Fe-Al system were obtained in various stoichiometric compositions. The different cooling rates of the casting led to two mechanisms of transformation into alpha-phase grains out of the unstable beta-phase, one being nucleation and growth producing needle-shaped grains, the other exhibiting a massive transformation into spherical grains.