Enhanced elasticity, fracture toughness and hardness in refractory TiZrHfNb high-entropy alloys by N- and O- doping engineering

Abstract

Nitrogen (N) and oxygen (O) doping have been considered as a new strategy to simultaneously improve the strength and fracture toughness/ductility of refractory TiZrHfNb high-entropy alloys (HEAs). Here, for the first time, we report the effects of N- and O- doping on the elasticity, fracture toughness and hardness of TiZrHfNb HEAs. Interestingly, the incorporation of N and/or O significantly enhances the elasticity and Vickers hardness of TiZrHfNb-based HEAs. More strikingly, the fracture toughness is enhanced by ∼33.3 %, and the hardness is simultaneously strengthened up to ∼10.4 % with the doping of 2.0 at% oxygen in TiZrHfNb-base HEAs. By contrast, the bulk modulus and shear rigidity show a monotonic increase with increasing N/O doping in (TiZrHfNb)_100-x-yO_xN_y HEAs. The enhancement in bulk and shear moduli is more pronounced for N-doped HEAs compared to O-doped ones, which is attributed to the larger lattice distortions in the N-doped HEAs. These findings offer new insights into the design and preparation of novel refractory HEAs and enrich the understanding of the strengthening mechanisms in light element-doped HEAs.