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 TiZrNbbased 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.