A superb mechanical behavior of newly developed lightweight and ductile Al0.5Ti2Nb1Zr1Wx refractory high entropy alloy via nano- precipitates and dislocations induced-deformation

The lightweight refractory high entropy alloys (RHEAs) can be considered the best alternative to Ni-based superalloys, which has significantly increased the attention of researchers. In this study, the newly designed lightweight (rho similar to 6.2 g/cm(3)) Al0.5Ti2Nb1Zr1WX (X: 0, 0.3, 0.5, 0.7) RHEAs were prepared. Our results evidence that the microstructure of Al0.5Ti2Nb1Zr1W0.5 RHEA has a BCC structure merged with B2 nano-precipitates, which leads to significant improvement in the specific yield strength (SYS) compared with other RHEAs. Besides, the compressive SYS (sigma(0.2)/rho) of Al0.5Ti2Nb1Zr1W0.5 RHEA at 298 K, 973 K, and 1078 K are as high as 187 MPa g(-1) cm3, 128 MPa g(-1) cm(3), and 95 MPa g(-1) cm(3), respectively. Interestingly, Al0.5Ti2Nb1Zr1W0.5 RHEA exhibited excellent ductility (greater than68 %) under compression at temperatures from 298 K to 1273 K. The distinct deformation mechanisms at 973 K and 1273 K are discussed as well. Initially, the strain hardening capability is provided by dislocation-dominated deformation. Conversely, with an increase in the strain, the micro-crack development and dynamic recovery (DRX) trigger the conversion from strain-hardening to persistent flow softening when the temperature is raised from 973 K to 1273 K. The persistent flow softening at 1273 K is primarily due to diffusion-controlled dislocation annihilation and continuous (DRX). (C) 2022 The Author(s). Published by Elsevier Ltd.

Automated summary

The lightweight refractory high entropy alloys (RHEAs) are considered as the best alternative to Ni-based superalloys, showing higher specific yield strength (SYS) and excellent ductility. The microstructure of Al0.5Ti2Nb1Zr1W0.5 RHEA, with a BCC structure merged with B2 nano-precipitates, plays a crucial role in its improved performance.