Hot deformation behaviour of AlCoCrFeNi2.1 eutectic high entropy alloy, consisting of fcc (CoCrFe-rich) and BCC (NiAl-rich) phases is studied by generating contour maps of multiple models using high temperature thermo-mechanical simulator compression test data. The workability regimes for thermomechanical processing are identified as 1073–1150 K and 10−3– 10−2.2s−1 as well as 1338–1373 K and 10−3–10−1.2 s−1. Finite element simulation has been used to study the strain distribution and material flow during hot deformation, which assists for predicting actual material flow in forging process. Flow instabilities during hot forming has been avoided by adopting integrated approach. © 2018 Elsevier B.V.

Phanikumar Gandham

Department of Metallurgical and Materials Engineering

M. R. Rahul

Sumanta Samal

S. Venugopal

Compression testing

Deformation

entropy

Eutectics

Forging

Hot Working

Finite element simulations

HIGH ENTROPY ALLOYS

Material flow

Processing maps

TRUE STRESS - TRUE STRAIN CURVES

finite element method

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Alloys and Compounds

Multicomponent Co25Fe25Mn5Ni25Ti20 eutectic high entropy alloy (EHEA), synthesized by vacuum arc melting followed by suction casting method resulted in two types of solid solution phases (fcc CoFeNi-rich (α) and bcc Ti-rich (β)) and Ti2(Ni, Co) type Laves phase. The hot deformation behaviours have been investigated at a temperature ranging from 1073 to 1273 K and different strain rates (10−3,10−2,10−1and 1 s−1). The optimum hot workability conditions of EHEA lies in temperature range 1073–1273 K and strain rate range 10−3 s−1-10−1.6 s−1 as well as temperature 1130–1225K and strain rate 10−0.5-1 s−1. The constitutive relation is established to understand the plastic deformability at high temperature. Finite element simulation has also been used to predict the deformation behaviour during the hot working process. © 2020 Elsevier B.V.

Hot workability of Co–Fe–Mn–Ni–Ti eutectic high entropy alloy

High entropy alloys with multiple phases are taken for undercooling studies and established the microstructure evolution with respect to undercooling. The melt fluxing technique was used for the current study to achieve undercooling. Predictions on the equilibrium phase formation of these systems was performed using CALPHAD approach and compared with experimental observations. Metastable microstructures were observed during undercooling and the morphological changes could be correlated with the currently established mechanisms. The detailed microstructure evolution in FeCoNiCuX0.5 (X = Al, Mo, Ti, W, Zr) shows the minute addition of these elements results in variation in microstructure evolution during as cast as well as undercooled condition. The studied systems show a maximum undercooling of more than 0.18 TL. and maintained crystalline nature even in deep undercooling. The segregation nature of elements was studied and correlated with the phase field simulations obtained. © 2019 Elsevier B.V.

Metastable microstructures in the solidification of undercooled high entropy alloys

In the design of high-entropy alloys (HEAs) with desired properties, identifying the effects of elements plays an important role. HEAs with eutectic microstructure can be obtained by judiciously modifying the alloy compositions. In this study, the effect of Nb addition to FeCoNiCuNbx (x = 0.5, 5, 7.5, 11.6, 15) alloys was studied by varying the Nb concentration (at.%). FeCoNiCuNb0.5 HEA shows liquid phase separation to form Cu-rich and FeCoNiCu-rich phases. Detailed solidification paths are proposed for these alloys, which show eutectic, peritectic, and pseudo quasi-peritectic reactions. Increasing Nb content promotes the liquid phase separation tendency and causes the formation of Cu-rich spheres. The effect of Nb on the FeCoNiCu-rich phase was studied based on the nanoindentation and correlated with nanohardness. The compressive deformation properties of these alloys are studied at room temperature and high temperature and correlated with microstructure. Fractography results show the mode of fracture and are correlated with the microstructure obtained. Copyright © Materials Research Society 2019.

Journal of Materials Research

Effect of niobium addition in FeCoNiCuNbx high-entropy alloys

A eutectic high-entropy alloy with seven components (Fe, Ni, Cr, V, Co, Mn, and Nb) was designed via the melt route guided by CALPHAD predictions. Configurational entropy estimated for the two-phase microstructure qualifies it to be referred to as a high-entropy alloy. When the Nb content exceeded 9.7 at. pct, the microstructure changed from hypoeutectic with primary face-centered cubic phase to hypereutectic with primary Laves phase. © 2019, The Minerals, Metals & Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Design of a Seven-Component Eutectic High-Entropy Alloy

Hot deformation behavior of equiatomic FCC CoCuFeMnNi complex concentrated alloy has been investigated via isothermal compression tests on Gleeble-3800 thermo-mechanical simulator in the temperature (T) range of 1073–1273 K and strain rate (ε˙) range of 1–10−3 s−1. This has been aided with detailed microstructural analysis using SEM, EBSD and TEM to decipher the deformation micro-mechanisms during hot compression tests. The processing maps have been constructed by superimposition of the instability map with efficiency map and the optimum thermo-mechanical processing conditions were found to be T = 1173 K, ε˙ = 10−3 s−1 and T = 1273 K, ε˙ = 10−2 s−1. Microstructural investigation using SEM and EBSD reveal phase separation between Cu-rich and Cu-lean regions wherein Cu-rich FCC phase at the grain boundaries undergoes discontinuous dynamic recrystallization (DDRX) while the Cu-lean phase undergoes dynamic recovery (DRV). The average activation volume in the range of 44–250 b3 suggest that cross slip is the rate controlling mechanism during the deformation and activation energy of 394 kJ/mol, that is almost twice than that for diffusion in copper, indicate contribution from both mechanical and thermal component to the overall activation energy. It is evident that the diffusion assisted copper segregation aids in obtaining higher efficiency of deformation and easy processability due to a unique microstructure comprising of Cu-lean grains surrounded by soft Cu-rich grains near grain boundaries which undergo DDRX. Numerical simulations using finite element method are able to correctly predict hot deformation behavior, establishing the processing-microstructure-property paradigm in CoCuFeMnNi complex concentrated alloy. © 2019 Elsevier B.V.

Materials Science and Engineering A

Establishing processing-microstructure-property paradigm in complex concentrated equiatomic CoCuFeMnNi alloy

Multi-component high entropy alloys (HEAs) are observed to form simple solid solutions in contrary to general perception that complex compounds may form in such multi-component equi-atomic alloys. In the present study, alloying behavior was investigated using XRD in AlCoCrCuFe and NiCoCrCuFe equi-atomic high entropy alloys synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). Simple FCC and BCC phases evolved after MA, while Cu-rich FCC and sigma (σ) phases evolved along with FCC and BCC phases after SPS. Further, NiCoCuFe, NiCoCrFe and NiCoFe equi-atomic alloys were investigated to confirm the formation of Cu-rich FCC, and σ phases. The hardness was observed to be 770 ± 10. HV for AlCoCrCuFe and 400 ± 10. HV for NiCoCrCuFe. Phase evolution after MA and SPS indicate that configurational entropy is not sufficient enough to suppress the formation of Cu-rich FCC, and σ phases, and enthalpy of mixing appears to play an important role in determining the phase formation in high entropy alloys after sintering. © 2011 Elsevier B.V.

Alloying behavior in multi-component AlCoCrCuFe and NiCoCrCuFe high entropy alloys

Materials & Design

A new strategy to design eutectic high-entropy alloys using simple mixture method

Journal of Materials Science & Technology

Effect of Niobium on Microstructure and Properties of the CoCrFeNb x Ni High Entropy Alloys

Materials Research Letters

Ultrafine-Grained AlCoCrFeNi2.1Eutectic High-Entropy Alloy

Reliability Engineering & System Safety

Rare event simulation in finite-infinite dimensional space

Experimental and finite element simulation studies on hot deformation behaviour of AlCoCrFeNi2.1 eutectic high entropy alloy

Journal	Data powered by TypesetJournal of Alloys and Compounds
Publisher	Data powered by TypesetElsevier Ltd
ISSN	09258388
Open Access	No