Unique deformation behavior and microstructure evolution in high-temperature processing of a low-density TiAlVNb2 refractory high-entropy alloy

Thermal deformation behaviors and microstructure evolution of a novel light refractory high-entropy alloy (RHEA) TiAlVNb2 were investigated in detail. Uniaxial compression was implemented at different strain rates from 10(-3) s(-1) to 10(-1) s(-1) and various temperatures from 1000 degrees C to 1200 degrees C. Stress-strain curves combined with electron back scattered diffraction analysis indicate that work hardening, dynamic re-crystallization (DRX) and dynamic recovery (DRV) occur during the thermal compression. Flow stress analysis carried out by the Arrhenius-type power law relationship suggests a high apparent activation energy of 401-375kJ.mol(-1) over the whole range of strain. The DRX acts as one of the main softening mechanisms, in which the DRX grains show a typical trend of increased size and fraction with increased temperature or/and decreased strain rate. Further analyses, however, reveal a unique DRX feature that both discontinuous and continuous DRX processes take place in this RHEA. The discontinuous DRX was proved by bulge (migration) of original grain boundaries, kernel average misorientation map and transmission electron microscopy; while the cumulative misorientation (point to origin) and the new grains formed at original grain interior support the existence of continuous DRX (CDRX). (C) 2021 Elsevier B.V. All rights reserved.