Effects of Cooling Rate on the Formation of Kappa Phase in the Cu-Al-Ni-Fe-Mn System

Aluminium bronzes of the complex type produced by the addition of Fe, Ni, and Mn in amounts of the order of 5%, 5% and 1% respectively, with Al close to 10% find wide-spread use as naval propeller material and in other marine applications. Their excellent properties are attributed to the transformation of the high temperature beta phase to an additional phase termed kappa in the alpha matrix. As the mode of formation of the kappa` phaseis reported to be influenced by the boqing rate,- which in turn affects the mechanical properties and corrosion resistance of the alloy, an attempt has been made to study the effects of coolings rates on the types, sizes, shapes, hardness and composition of the kappa phase using, metall-ographic techniques and microprobeanalysis.