Microstructure and properties of novel CoCrFeNiTax eutectic high-entropy alloys

Eutectic high-entropy alloys are potential replacements of structural alloys, due to their microstructure and properties. In this work, CoCrFeNiTax (x = 0.1, 0.2, 0.3, 0.395, 0.4 and 0.5, x value in molar ratio) eutectic high-entropy alloys were produced by arc melting technique. Two phases, FCC solid solution and Laves phase, are identified in the alloys. The alloys are transformed from hypoeutectic to hypereutectic solidification by increasing Ta content. CoCrFeNiTa0.395 eutectic high-entropy alloy exhibits an ultrahigh yield strength of 1.4 GPa, while CoCrFeNiTa0.3 hypoeutectic high-entropy alloy shows a compressive strength of 2.5 GPa and a considerable fracture strain of 44%. Such remarkable strengthening effects are shown to result from the ideal combination among the second-phase, solid solution, and boundary strengthening.