Microstructure and mechanical properties of CoCrFeNiZrx eutectic high-entropy alloys

Abstract The emergence of eutectic high-entropy alloys containing Laves phase provides a new and exciting research direction towards developing advanced structural alloys, in light of the inherent advantages of Laves phase at elevated temperatures. In this work, CoCrFeNiZrx alloys were prepared with varying zirconium contents by vacuum arc-melting method. Typical eutectic microstructure was identified in the as-cast alloy having x = 0.5. The alloys consist of face-centered cubic solid solution and C15 Laves phase in the form of lamellae. Crystallographic orientation relationship between these two phases was determined. With the increase of the volume fraction of hard C15 Laves phase, the resulting alloys showed an increase in strength, but became more brittle at room temperature; the fracture process changed from ductile inter-lamellar fracture to brittle trans‑lamellar fracture. With the increase of test temperature, however, the fracture mode converted to be ductile fracture. As such, the eutectic microstructure can accommodate considerable plastic strain and has potential for engineering applications involving elevated temperatures.