Do intermetallics interfere with the martensitic reaction in Cu-rich alloys?

The presence of intermetallic compounds (IMCs) on the microstructure of some Cu-based materials, such as shape memory alloys and nickel-aluminum bronzes, affects their properties. Moreover, both groups of materials can present martensitic transformation after proper heat treatment. Optical microscopy with unpolarized and polarized light, electron scanning microscopy with secondary and backscattered electrons detectors, energy-dispersive X-ray spectroscopy, and differential scanning calorimetry were employed to evaluate if the presence of intermetallics on the microstructure of three Cu-rich ternary Cu-Al alloys can interfere with the martensitic reaction. Results suggested that Al-rich IMCs hamper this phase transition, while Cu-rich ones have the opposite effect. In addition, the ternary additions also modified the martensite decomposition from the binary alloy used as a reference in this work and the IMCs cannot be dissolved during the heating before quenching. Finally, it was found that differences in electronegativity values and atomic radius between the ternary addition, Cu, and Al atoms are correlated with the chemical composition from the IMC and its thermal stability range, being useful parameters for the prediction of the microstructure from the analyzed materials.