INFLUENCE OF THE THERMAL VARIABLES OF SOLIDIFICATION ON THE MICROSTRUCTURE AND PROPERTIES OF THE Cu-24Zn-6Al-4Mn-3Fe ALLOY
The conditions used during the solidification process of a metal affect the microstructural characteristics of the material, such as: dendritic spacing, heterogeneity of chemical composition and phase formation. As consequence of these variations, the mechanical, chemical and physical properties are also altered. This study aims to evaluate the influence of the solidification thermal variables of the alloy Cu-24Zn-6Al-4Mn-3Fe. The alloy was solidified in a device with an ascending heat flow system, and the heat was extracted through a water-cooled ABNT 1020 steel interface. After the acquisition of the solidified material, it was subjected to cuts via wire EDM for analysis at each position of the thermocouples. The microstructure was analyzed by optical microscopy, scanning electron microscopy and x-ray diffraction in order to characterize the phases and intermetallics present in the material. The macrographic analysis showed a fully refined structure without the presence of column grains due to the addition of iron. The mechanical properties were evaluated by means of hardness, microhardness and wear tests along the entire longitudinal extension of the solidified part, whereas the corrosion analysis was performed by the linear polarization and cyclic voltammetry methods. All analyzes were correlated with thermal solidification variables in order to understand their influence on the behavior of the alloy studied. The results showed that when moving away from the heat exchange base, there is an increase in hardness and microhardness, this may be correlated with the increase in intermetallics with the decrease in the cooling rate, as analyzed via scanning electron microscopy. Furthermore, in all positions there was no significant change in the amount of α phase retained and, therefore, the matrix is composed mostly of β phase with approximately 2% of α phase.