Oxygen-assisted spinodal structure achieves 1.5 GPa yield strength in a ductile refractory high-entropy alloy

摘要

Refractory high-entropy alloys(RHEAs)with room-temperature ductility are drawing growing attention for potential high-temperature applications.However,the most widely used metallurgical mechanisms appear weak in optimizing their strength and ductility.Here,we report that the nanoscale spinodal struc-ture in Ti_(41)V_(27)Hf_(15)Nb_(15)O_(2)leads to the highest tensile yield strength(∼1.5 GPa)among the existing RHEAs and good elongation of∼12%.With the aid of thermodynamic calculations,we show that oxygen plays a dominant role in controlling the formation of the spinodal structure by influencing the spinodal gap of the Ti-V-Hf-Nb system.Exploring the atomic structure of the spinodal structure(β+β^(∗)),we showed that the large lattice misfit of the spinodal phases is mainly responsible for the excellent strengthen-ing effect while the planar to wavy dislocation glide mode transition accounts for the retained ductility.This work provides a novel strategy to improve the mechanical properties of the RHEAs and deepens the understanding of their phase stabilities.