The Microstructural Evolution and Mechanical Properties of Boron-Doped Ti35Zr30V10Nb25 Refractory High-Entropy Alloy

The addition of oxygen or nitrogen in refractory high-entropy alloys (HEAs) has been widely reported, but studies on boron-doped HEAs have mainly focused on the segregation of boron elements at grain boundaries. The changes in the microstructure and mechanical properties in TiZrNb-based HEAs remain enigmatic. In this work, boron-doped Ti35Zr30V10Nb25 (Ti35-xB) refractory HEAs were designed to elucidate their microstructural evolution and mechanical properties. Unlike oxygen and nitrogen, trace amounts of boron addition result in the formation of borides, and boron exhibits a strong repulsion towards Zr, leading to Zr-depleted borides. Borides distributed along the grain boundaries refine the grain size and dendritic structure. The borides and structural refinement effect enhance the strain-hardening capacity and uniform elongation, resulting in an over 15% uniform elongation for Ti35-0.25B.