Dami Yim

Constitutive modeling of deformation behavior of high-entropy alloys with face-centered cubic crystal structure

ABSTRACT A constitutive model based on the dislocation glide and deformation twinning is adapted to face-centered cubic high-entropy alloys (HEAs) as exemplified by the CrMnFeCoNi system. In this model, the total dislocation density is considered as the only internal variable, while the evolution equation describing its variation during plastic deformation is governed by the volume fraction of twinned material. The suitability of the model for describing the strain hardening behavior of HEAs was verified experimentally through compression tests on alloy CrMnFeCoNi and its microstructure characterization by electron backscatter diffraction and X-ray diffraction using synchrotron radiation. GRAPHICAL ABSTRACT IMPACT STATEMENT We adopted a constitutive model based on dislocation density and twin volume fraction evolution, to analyze the deformation behavior of the high-entropy alloy CrMnFeCoNi theoretically.

On the strain rate-dependent deformation mechanism of CoCrFeMnNi high-entropy alloy at liquid nitrogen temperature

ABSTRACT In the present work, the deformation mechanisms of the CoCrFeMnNi high-entropy alloy at 77 K were investigated using thermal activation analyses. The strain rate jump test was performed to estimate strain rate sensitivity and the activation volume of the alloy. Transmission electron microscopy analyses were performed to identify the evolution of twins at low temperatures. The insensitivity of activation volume to strain observed in the CoCrFeMnNi alloy at 77 K was different from the observed increase in the activation volume with strain at room temperature, which occurred due to the shearing of nanoscale inhomogeneities, such as co-clusters and short-range orders. GRAPHICAL ABSTRACT IMPACT STATEMENT The insensitivity of the activation volume to plastic strain in the CoCrFeMnNi alloy at 77 K can be attributed to the increasing fraction of mechanical twinning with strain.

Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.

Data to reproduce and modify “An approach for screening single phase high-entropy alloys using an in-house thermodynamic database”

XRD raw data of the milled and heat-treated Co,Fe,Mn,Ni,Zn-containing high-entropy alloys (HEAs) is presented. Complete description of the quaternary, quinary and senary binary priority lists, including the names of the most relevant binary sets of elements for solid solution screening and the details of the parametric criterion used for making these lists are offered alongside a detailed thermodynamic description used to design Co,Fe,Mn,Ni,Zn-containing HEAs. In addition, a complete parametric study for quaternary, quinary and senary HEAs is shown. All the files and codes necessary to replicate and modify the previously mentioned results are available; commented by the authors in order to facilitate their usage. For further interpretation follow the research article: An approach for screening single phase high-entropy alloys using an in-house thermodynamic database (Tapia et al., 2018).