Synergistic increasing the Strength–Elasticity in a CoNiV medium-entropy alloy via cold drawing

Abstract

The development of high-performance ultraelastic metals with exceptional strength and large elastic strain limits is critical for a wide range of industrial applications, including actuators, medical devices, and high-precision instruments. In this study, a novel strategy is proposed to construct a dual-phase lamellar heterogeneous structure in a CoNiV medium-entropy alloy (MEA) by pre-introducing a precipitated phase prior to cold drawing. This structure, composed of elongated κ phases and an FCC matrix, enables an outstanding combination of an ultrahigh tensile strength (2.6 GPa) and an elastic strain limit of 1.5 %. The cold-drawing performance of the CoNiV MEA containing the brittle κ phase is significantly enhanced by the pronounced twinning-induced plasticity (TWIP) effect and the transformation-induced plasticity (TRIP) effect (κ → FCC). The dual-phase lamellar structure effectively disperses cracks and delays stress concentration, contributing to high crack tolerance. Meanwhile, the presence of high dislocation density, fine grain size, residual κ phases, and various nanoscale defects imparts the alloy with exceptional strength. This work innovatively addresses the general limitation of elastic strain in high-strength materials through multi-phase structural design, offering new theoretical insights and a design paradigm for the development of advanced metallic materials with superior strength and elastic deformability.