High entropy component-induced nanoscale shear banding and twinning enhance Ti6Al4V alloy surface properties

Abstract

High-entropy alloys (HEAs) present unique advantages in surface modification due to their stable mixed-state structures and resistance to intermetallic compound formation. This study investigates the surface modification behavior of equiatomic TiNbHfZnZr HEA components in Ti6Al4V alloy using friction stir processing (FSP). The aim is to enhance the mechanical properties and structural stability of Ti6Al4V by incorporating HEA elements. It was found that the introduction of high-entropy alloys forms shear bands with distinctive micro and nano gradient structures on the surface of the Ti6Al4V alloy. These shear bands not only significantly refine the grains but also promote β phase and β twin formation. The HEA-induced shear bands enhance the strength and stability of the alloy by creating bcc twins and dislocation networks that suppress martensitic transformation and maintain superelasticity. Concurrently, the introduction of HEA components leads to the formation of stable dual-phase (α + bcc) microstructures within the α matrix, significantly improving hardness and modulus.