Second Phase of 29Fe15Al18Cr27Ni High-Entropy Alloy

Abstract

In this study, a FeNiAlCr four-element high-entropy alloy of grain size 2–3 μm was prepared using the vacuum induction furnace. The yield limit of the alloy reached 550 MPa at the room temperature. There were two second-phases in the alloy , namely the geometric dense-packing phase (GCP) and topological dense-packing phase (TCP). Fe₃Ni₂ with face-centered cubic (FCC) structure was the matrix phase. A chain-like geometric dense-packed phase was formed at the grain boundary of the matrix: Ni₃Al phase (γ’), while a topological dense-packed phase, FeCr(σ), was distributed in the matrix grain. The intergranular ductile fracture of the alloy under stress was resulted from the interaction of the two phases. As Ni₃Al was coherent with the matrix and dispersive homogeneous nucleation , it was the main strengthening phase in the alloy . The metallographic morphology of FeCr phase was granular and was the channel of crack generation and propagation. FactSage 6.2 was used to calculate the formation and decomposition of the phases in the alloy . Ni₃Al and FeCr were formed from the alloy when it was cooled to about 600 °C, and the two phases almost occurred at the same time. The differential scanning calorimeter (DSC ) results confirmed this conclusion.