Regulate local chemical order to achieve high strength and ductility in TiZrNbVAl lightweight high entropy alloys via adding oxygen

TiZrNbVAl lightweight high-entropy alloys (LHEAs) with body-centered cubic (BCC) structure have received extensive attention due to their low density and considerable mechanical properties. And the mechanical properties of these LHEAs can be further improved by adjusting the local chemical order (LCO). Here, we report a strategy for regulating LCOs in TiZrNbVAl LHEAs by adding oxygen. The results showed that the yield strength of LHEA increased from 787.8 MPa to 1029.5 MPa after oxygen addition. Moreover, the microstructure evolution proves that LCOs is conducive to promoting the transition of dislocation from plane slip, which is easy to produce stress concentration, to multistage slip, which improves the homogenizing deformation ability, and increasing the ductility from 12.8 % to 20.9 %, which is an increase of ∼63 %. Our work provides a paradigm for achieving outstanding strength-ductility tradeoff in BCC-LHEAs via O doping.