Phase stability and unidirectional solidification in a Ni–Al bronze

Abstract

CuAlFeNi alloys are considered very important from the commercial point of view to exhibit different phase transitions and properties, depending on the relationship among these phases. We investigated the stability of different formed phases after slow cooling, as well as after unidirectional solidification of the Cu-10.79 wt%Al-4.42 wt%Ni-3.67 wt%Fe alloy, establishing the effects of changes in the amounts of phases on material characteristics. The analysis was performed using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, hardness measurements, differential scanning calorimetry, and potentiodynamic polarization tests. The data revelated that the Ni and Fe increased the β phase stability. Obtained samples after unidirectional solidification exhibited a higher fraction of α phase when compared to the same alloy after slow cooling. It also was verified that the corrosion resistance is dependent on the position of the sample concerning the heat exchange surface.