Natural-mixing guided design of refractory high-entropy alloys with as-cast tensile ductility

TL;DR

This study introduces a novel refractory high-entropy alloy (RHEA) with over 20% tensile ductility in the as-cast state, leveraging natural-mixing tendencies to enhance high-temperature stability and mechanical properties.

Contribution

The paper presents a new RHEA design using natural-mixing characteristics, achieving high ductility and stability without complex processing.

Findings

Achieved >20% tensile ductility in as-cast RHEA

Identified beta prime precipitation as strengthening mechanism

Demonstrated physicochemical stability at high temperatures

Abstract

Multi-principal-element metallic alloys have created a growing interest that is unprecedented in metallurgical history, in exploring the property limits of metals and the governing physical mechanisms. Refractory high-entropy alloys (RHEAs) have drawn particular attention due to their (i) high melting points and excellent softening-resistance, which are the two key requirements for high-temperature applications; and (ii) compositional space, which is immense even after considering cost and recyclability restrictions. However, RHEAs also exhibit intrinsic brittleness and oxidation-susceptibility, which remain as significant challenges for their processing and application. Here, utilizing natural-mixing characteristics amongst refractory elements, we designed a Ti38V15Nb23Hf24 RHEA that exhibits >20% tensile ductility already at the as-cast state, and physicochemical stability at high-temperatures. Exploring the underlying deformation mechanisms across multiple length-scales, we observe that a rare beta prime precipitation strengthening mechanism governs its intriguing mechanical response. These results also reveal the effectiveness of natural-mixing tendencies in expediting HEA discovery.