LAUSR

There has been great attention on high-entropy alloys (HEAs) over the past decade. Unlike conventional alloy systems, HEAs commonly include at least five principal elements with equiatomic or near-equiatomic ratio. HEAs with their superior mechanical, magnetic, and thermal properties are promising materials for critical engineering applications. Medium-entropy alloys (MEAs), which consist of less than five principal elements, have very similar structural features with HEAs such as robust thermodynamic stability and exceptional mechanical performance. The insights of MEAs have not been fully revealed yet. In the present study, novel MEAs (Cu 20 Ni 20 Al 30 Ti 30 , Cu 25 Ni 25 Al 25 Ti 25 , Cu 34 Ni 22 Al 22 Ti 22 , and Cu 35 Ni 25 Al 20 Ti 20 ) have been designed using thermo-physical calculations and Thermo-Calc software. These MEAs were then produced using copper heart arc melting and suction cast into cylindrical rods with 3 mm diameters. X-ray diffraction (XRD), optical microscope (OM), transmission electron microscope (TEM), scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) were used for structural characterization. The corresponding results reveal that the Cu 20 Ni 20 Al 30 Ti 30 , MEA, consists of a body-centered cubic (BCC-B2) phase with intermetallic compounds (ICs), whereas Cu 25 Ni 25 Al 25 Ti 25 has single BCC-B2 phase. When the amounts Cu and Ni are increased, system drives itself toward a face-centered cubic (FCC) structure. A dual BCC and FCC composite Cu 35 Ni 25 Al 20 Ti 20 has been detected as the most promising MEA among the others with 820 and 1338 MPa measured yield and compressive strength, respectively.