Size matters: Influence of atomic radius from the ternary addition on the properties of Cu79Al19X2 (X = Be, Mn, Ag) alloys

Cu-rich alloys from the Cu-Al-Be, Cu-Al-Mn, and Cu-Al-Ag systems share the shape memory effect and other important properties, as well as some limitations to their application. However, the role of the atomic radius from the ternary additions on these properties remains unknown. Cu79Al19X2 (X = Be, Mn, Ag) alloys were charac-terized and compared with the Cu81Al19 alloy to evaluate which properties can be altered due to change in the atomic radius from the ternary addition. Differential thermal analysis, differential scanning calorimetry, Vickers microhardness, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction with Rietveld refinement, resistivity measurements, and quantitative metallography were performed for this purpose. The results showed that critical temperatures and rate of melting and eutectoid phase transi-tions, the tendency for ordering, the microhardness, and the electrical resistivity from the Cu-rich solid solution are responsive to the change in atomic radius from the ternary addition. Furthermore, all ternary additions resulted in hampering of alpha phase ordering, delay of the beta phase decomposition, and decrease in the grain boundary surface. The intensity of all these phenomena can also be related to the variation of the atomic radius from the ternary addition.