Phase transformation assisted twinning in a face-centered-cubic FeCrNiCoAl0.36 high entropy alloy
Journal
Acta Materialia
Journal Volume
181
Start Page
491
End Page
500
ISSN
13596454
Date Issued
2019
Author(s)
Yu, Peijun
Feng, Rui
Du, Junping
Shinzato, Shuhei
Chen, Bilin
Lo, Yu-Chieh
Liaw, Peter K.
Ogata, Shigenobu
Hu, Alice
Abstract
The FeNiCoCr-based high entropy alloys (HEAs) exhibit excellent mechanical properties, such as twin-induced plasticity (TWIP) and phase transformation plasticity (TRIP) that can reach a remarkable combination of strength and ductility. In the present work, the face-centered-cubic (FCC) single-crystal FeNiCoCrAl0.36 HEAs were studied, using the density functional theory (DFT) combined with the phonon calculation to estimate the stacking fault energies, temperature-dependent phase stabilities of different structures. And the kinetic Monte Carlo (kMC) was used to predict the substructures evolution based on the transition state energies obtained from DFT calculations. We proposed two different formation paths of nano-twins in this Al-composited HEA and found that short-range hexagonal-close-packed (HCP)-stacking could occur in this HEA. The DFT calculations suggest that this HEA has negative stacking fault energy (SFE), HCP formation energy, and twin-formation energy at 0 K. Phonon calculations indicate that at the finite temperature, the competing FCC/HCP phase stability and propensity for twinning make it possible to form HCP-like twin boundaries. The kMC simulations suggest that under deformation, TWINs could form within the HCP laths which differs from the study of others. With the great agreement of results from kMC simulations and experiments, this twin-hcp laminated substructure formation path offers a new concept of designing TWIP HEAs containing tunable twin structures with HCP and TWIN lamellae structures, which could result in better mechanical properties of HEAs. © 2019 Acta Materialia Inc.
Subjects
First principles
High entropy alloy
Kinetic Monte Carlo
Phase transformation
Twinning
Publisher
Acta Materialia Inc
Type
journal article