The mechanism of multi-component dislocation synergistic evolution and material strengthening in the as-cast TiZrNbV refractory high-entropy alloy

Abstract

High/medium-entropy alloys (HEAs/MEAs) are gaining attention for their superior mechanical properties, especially in applications that require high strength and impact resistance. Among these, body-centered cubic (BCC) refractory HEAs are notable for their high-temperature stability and mechanical strength. However, achieving an optimal balance between strength and ductility remains challenging. This study focuses on TiZrNbV BCC-HEA, which exhibits not only impressive strength (yield strength > 1 GPa) but also good ductility (∼9 % uniform elongation). Its plastic deformation and strengthening mechanisms are investigated through uniaxial tensile tests, cyclic load-unload-reload tests, and stress-relaxation tests. Key to understanding its mechanical behavior is the evolution of dislocation structures, including mobile dislocations, geometrically necessary dislocations (GNDs), and statistically stored dislocations (SSDs). The Kocks-Mecking model is employed to examine hardening mechanisms. At low strains, heterogeneous deformation-induced (HDI) hardening dominates, while forest dislocation hardening prevails at higher strains. This work sheds light on the interplay of dislocation density evolution and hardening mechanisms in achieving the high strength and ductility of alloys. These mechanisms of dislocation synergistic evolution and strengthening are valuable for designing advanced alloys with optimized mechanical properties, paving the way for high-performance materials in extreme environments like aerospace, automotive, and energy industries.