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

Abstract

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 (ρ ∼ 6.2 g/cm3) 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 (σ0.2/ρ) 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 cm3, and 95 MPa g−1 cm3, 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).