On the short-time thermal phase-stability of as-cast AlCoCrFeNi2.1 eutectic high entropy alloy

The present work deals with the short-time thermal phase-stability of the as-cast eutectic AlCoCrFeNi2.1 high entropy alloy. Toward this end, the effect of different temperatures (800-1000 degrees C) and soaking times (15-60 min) on the stability of primary dendritic regions and formation of the ordered phases was explored. Microstructural characterization was supported by thermodynamic calculations and assessment of the subsequent mechanical properties. Upon the increase in annealing temperature and soaking time, the primary FCC dendritic areas grown and destabilized owing to elemental partitioning. This was followed by dendrite fragmentation and formation of needle shape B-2 ordered phases within the primary FCC regions. Despite the unstable nature of the primary constituent phases, the material hardness increased considerably to a peak point corresponding to the moderate soaking time of 45 min. The variation of the subsequent mechanical properties was discussed relying on the characteristics of the ordered and primary phases. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

This study investigates the short-time thermal phase-stability of the as-cast eutectic AlCoCrFeNi2.1 high entropy alloy. Microstructural characterization, thermodynamic calculations, and assessment of mechanical properties were conducted to explore the effect of different temperatures and soaking times on the stability of primary dendritic regions and the formation of ordered phases. The results show that the primary dendritic regions grow and destabilize with an increase in annealing temperature and soaking time, leading to the formation of needle shape B-2 ordered phases. Despite the unstable nature of the primary constituent phases, the material hardness increases significantly at a moderate soaking time.