Effects of Thermal Variables of Solidification on the Microstructure, Hardness, and Microhardness of Cu-Al-Ni-Fe Alloys

Aluminum bronze is a complex group of copper-based alloys that may include up to 14% aluminum, but lower amounts of nickel and iron are also added, as they differently affect alloy characteristics such as strength, ductility, and corrosion resistance. The phase transformations of nickel aluminum-bronze alloys have been the subject of many studies due to the formations of intermetallics promoted by slow cooling. In the present investigation, quaternary systems of aluminum bronze alloys, specifically Cu-10wt%Al-5wt%Ni-5wt%Fe (hypoeutectoid bronze) and Cu-14wt%Al-5wt%Ni-5wi%Fe (hypereutectoid bronze), were directionally solidified upward under transient heat flow conditions. The experimental parameters measured included solidification thermal parameters such as the tip growth rate (V-L) and cooling rate (T-R), optical microscopy, scanning electron microscopy (SEM) analysis, hardness, and microhardness. We observed that the hardness and microhardness values vary according to the thermal parameters and solidification. We also observed that the Cu-14wt%Al-5wt%Ni-5wi%Fe alloy presented higher hardness values and a more refined structure than the Cu-10wt%Al-5wt%Ni-5wt%Fe alloy. SEM analysis proved the presence of specific intermetallics for each alloy.