Achieving outstanding strength-ductility matching in BCC light-weight high entropy alloys via high content ordered nanoprecipitates

The body-centered cubic (BCC) lightweight high entropy alloys (LHEAs) have attracted much attention owing to their remarkable mechanical properties. Coherent ordered nanoprecipitation (CON) hardening is an effective strategy to break the strength-ductility trade-off, where achieving a high content of CON with disperse distribution is a key factor. In this work, we selected the BCC Ti–Zr–V–Nb–Al system as the LHEA model. By adjusting the composition, the lattice mismatch between B2–CON and matrix was well kept at a low level (∼0.2%) to ensure the disperse distribution of the high content B2–CON. Moreover, the formation of other harmful precipitates was effectively avoided by using the low temperature heat treatment with fast cooling. As a result, high content (∼65%) B2–CON with disperse distribution was obtained in Ti–Zr–V–Nb–Al LHEAs, generating a significant strength increasement of ∼430 MPa (∼41% of the total strength), and retaining considerable ductility (∼16%). This study provides an effective approach to develop the CON strengthened LHEA with excellent strength and ductility.