Excellent thermal stability and mechanical properties of bulk nanostructured FeCoNiCu high entropy alloy

Abstract

In this work, we report bulk nanostructured equiatomic FeCoNiCu high-entropy alloy (HEA) with superior thermal stability and decent mechanical properties. High pressure torsion (HPT) was employed to refine the grains in the HEA into nanoscale (80 nm), and then Cu-rich particles were in-situ introduced at grain boundaries by subsequent annealing (≥700 °C), forming a multi-phase nanostructure. The Cu-rich particles are highly stable at high temperatures and impose a pinning effect on the grain boundaries, which significantly restricts grain growth (grain size <500 nm up to 900 °C), thus leading to outstanding thermal stability. On the other hand, the nanostructures also possess high yield strengths of 643∼1165 MPa, mainly attributing to grain boundary hardening. Meanwhile, the in-situ formed Cu-rich particles can concurrently deform with the matrix during straining, resulting in large total elongation (15∼20%). This work provides a novel strategy for designing bulk nanostructured HEA with good thermal stability and mechanical properties.