The effects of chemical disorder and external loading conditions on the structural transformation between HCP and FCC phases in CrCoFeNi high-entropy alloys: a first-principles study

The influences of chemical disorder and external loading conditions on the reversible structural transformation between hexagonal close-packed (HCP) and face centred cubic (FCC) phases in CrCoFeNi high entropy alloys (HEAs) are studied from first-principles calculations. The generalised planar fault energy curves are utilised to analyse the competition between the transformation and deformation twining in the HEA. It is found that the transformation-induced plasticity (TRIP) could occur in CrCoFeNi HEA through the reversible HCP-to-FCC transformation under hydrostatic pressures or uniaxial tensions, which is enhanced in the regions with high or low local concentration of Co or Ni, respectively. These findings well explain on the TRIP in CrCoFeNi HEAs from an energetics perspective, and provide useful information on the effects of chemical disorder on dislocation activities in HEAs. The results reported in this work could facilitate the development of HEAs with structural transformation accommodated plasticity.