Intrinsic edge dislocations promote high-temperature strength and ductility in additively manufactured refractory high-entropy alloys

Abstract

Abstract Refractory high-entropy alloys (RHEAs) hold promise for applications in extreme environments. However, conventional as-cast RHEAs are constrained by the trade-off between strength and ductility, necessitating time- and energy-intensive post-processing. Here, we propose a streamlined strategy to fabricate RHEAs via laser directed energy deposition (LDED) using elemental powder blends, eliminating the need for post heat treatments. The additively manufactured (AMed) Nb 40 Ta 25 Ti 15 Hf 15 Zr 5 alloy, characterized by a high density of intrinsic edge dislocations introduced during the thermal cycling of the process, demonstrates a remarkable tensile strength of ~497.3 MPa and a uniform elongation of ~6.8 % at 1000 °C, representing a ~ 37.8% and ~61.9% increase, respectively, over its as-cast counterparts. It is found that the intrinsic edge dislocations generated during AM process significantly enhances the alloy’s strain hardening capability at elevated temperatures. Simultaneously, the high density of edge dislocations effectively enhance material deformability through kink band formation and the stochastic nature of dislocation motion. This work presents a cost-effective pathway for the rapid fabrication of AMed RHEAs with an exceptional combination of high-temperature strength and ductility, paving the way for next-generation structural alloys in extreme environments.