Enhanced Elasticity, Fracture Toughness and Strength 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 N- and O- doping effects on the elasticity, fracture toughness and strength of refractory TiZrHfNb HEAs. It is found that the doping of nitrogen and/or oxygen results in the enhancement in elasticity, Vickers hardness and strength in TiZrHfNb-base HEAs. Interestingly, the fracture toughness is enhanced by approximately ~33.3%, and the yield strength is simultaneously strengthened up to ~10.4% with the addition of 2.0 at% oxygen in TiZrHfNb-base HEAs. By contrast, the bulk modulus and shear rigidity exhibit a monotonic increase with increasing N and O content in (TiZrHfNb)100-x-yOxNy HEAs, whereas the enhancement in bulk and shear moduli for N-doped HEAs is more pronounced than the O-doped ones which can be attributed to the larger lattice distortions in the N-doped HEAs. These new results and findings provide new insight into designing and preparing novel refractory high-entropy alloys, and understanding the strengthening mechanism of light element-doped HEAs.

Keywords: Elasticity, Fracture toughness, Vickers hardness, Yield strength, TiZrHfNb High-entropy alloys