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.

Phanikumar Gandham

Department of Metallurgical and Materials Engineering

M. R. Rahul

Sumanta Samal

Cobalt alloys

entropy

Eutectics

FRACTURE MECHANICS

HIGH-ENTROPY ALLOYS

Iron alloys

microstructure

nanoindentation

Niobium

Phase separation

Plastic flow

Solidification

Alloy compositions

COMPRESSIVE DEFORMATIONS

Effect of niobium

EUTECTIC MICROSTRUCTURE

LIQUID PHASE SEPARATION

MODE OF FRACTURE

PERITECTIC REACTION

SOLIDIFICATION PATHS

Copper alloys

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 Materials Research

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.

Journal of Alloys and Compounds

Metastable microstructures in the solidification of undercooled high entropy alloys

Studies on solidification of equiatomic multi-component alloys are essential in developing melt-route processing of high entropy alloys. The extent of undercooling during processing controls microstructure evolution. In this study, we present solidification studies on undercooled equiatomic FeCuNi alloy carried out using melt fluxing technique. The alloy shows a two-phase (FCC + FCC) microstructure even at deep undercooling of more than 200 K. The dendrite growth velocity measured using high-speed video imaging shows a nonlinear increase in growth velocity with the increase in the extent of undercooling. A modified dendritic growth model was able to predict the growth velocity. The segregation behaviour and microstructures at different extents of undercooling can be predicted using phase field simulation. © 2019 Elsevier B.V.

Solidification behaviour of undercooled equiatomic FeCuNi alloy

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.

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

Multicomponent Co20Cu20Fe20Ni20Ti20 eutectic high entropy alloy (HEA), processed by vacuum arc melting cum suction casting technique was studied. The microstructure of this eutectic HEA consists bcc (β) and fcc (α2) solid solution dendritic phases and eutectics (fcc (α1) plus Ti2(Ni, Co)-type Laves phase). Serrations in the flow behaviour are attributed to multi substitutional solutes in the multi-phase microstructure. Based on the detailed analysis of mechanical data together with deformed microstructural characterization, the optimum thermo-mechanical processing conditions for hot working are identified as T=930-990 °C (1203-1263 K) and strain rate range of 10-3 s-1-10-1 s-1. © 2016 Elsevier B.V.

Materials Science and Engineering A

Hot deformation behaviour and processing map of Co-Cu-Fe-Ni-Ti eutectic high entropy alloy

The decomposition of an equiatomic AlCoCrCuFeNi high-entropy alloy produced by splat quenching and casting was investigated by the analytical high resolution methods: transmission electron microscopy and three-dimensional atom probe. It could be shown that splat-quenched alloy consisted of an imperfectly ordered body-centred cubic phase with a domain-like structure, whereas normally cast alloy formed several phases of cubic crystal structure. The cast alloy decomposed into both dendrites and interdendrites. A detailed local compositional analysis carried out by atom probe within the dendrites revealed that the alloying elements in the Ni-Al-rich plates and Cr-Fe-rich interplates are not randomly distributed, but segregate and form areas with pronounced compositional fluctuations. Cu-rich precipitates of different morphologies (plate-like, spherical and rhombohedron-shaped) could also be found in the dendrites. The results are discussed in terms of segregation processes governed by the enthalpies of mixing of the binary systems. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Acta Materialia

Decomposition in multi-component AlCoCrCuFeNi high-entropy alloy

A superfine eutectic microstructure and the mechanical properties of CoCrFeNiMox high-entropy alloys

Materials Science and Engineering: A

Phase stability and mechanical properties of AlHfNbTiZr high-entropy alloys

Effect of niobium addition in FeCoNiCuNbx high-entropy alloys

Journal	Data powered by TypesetJournal of Materials Research
Publisher	Data powered by TypesetCambridge University Press
ISSN	08842914
Open Access	No