Determination of microstructural properties and its effects on hardness of FeNiCrCoAlx (x=0,20 at%) high entropy alloys

Determination of microstructural properties and its effects on hardness of FeNiCrCoAlx (x=0,20 at%) high entropy alloys

Poluru, Madhav (TU Delft Mechanical, Maritime and Materials Engineering)

Sietsma, J. (mentor)

Delft University of Technology

Mechanical Engineering

2017-08-24

In recent years, the concept of high entropy alloys (HEAs) has gained increasing attention due to their unique compositions, microstructures and properties. High entropy alloys are defined as solid-solution alloys with 5 or more principal elements in equal or nearly equal atomic fractions with the elemental concentrations ranging from 5 – 35at%. This new class of materials are considered to be potential alternatives to the conventional materials which are currently being used in the different fields such as structural, nuclear, automotive and aerospace industries.
In this study, the determination of phases and microstructural properties of FeNiCrCo and FeNiCrCoAl high entropy alloys with nearly equi-atomic concentrations and their influence on the hardness of the material after undergoing different thermo-mechanical treatments was studied. The combination of different techniques such as, X-ray diffraction (XRD), Energy dispersive spectroscopy (EDS) and Electron backscattered diffraction (EBSD) were used to determine the phases present in the alloy systems for different experimental conditions. Optical microscopy, scanning electron microscope (SEM) were used to observe the microstructural evolution in the material. Vickers hardness tester is used to determine the hardness values.
FeNiCrCo high entropy alloy system was found out to be a single-phase FCC system for all experimental conditions whereas FeNiCrCoAl contains a mixture of BCC, FCC and Sigma phases. The hardness values were correlated to the phases present and the microstructural properties of the alloy. This study provides an overview of the behavior of these alloy systems from intermediate to high temperature range for two different starting conditions, as cast and hot rolled. This work can be considered as a first step to fully understanding the potential of these high entropy alloy systems to serve as potential alternatives to the conventional alloys currently used.

High Entropy Alloys

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Student theses

master thesis

© 2017 Madhav Poluru