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An Experimental Investigation: Microstructure and Mechanical Properties of Directed Energy Deposited AlCuFeNiTi High Entropy Alloy /

Record Type:	Electronic resources : Monograph/item
Title/Author:	An Experimental Investigation: Microstructure and Mechanical Properties of Directed Energy Deposited AlCuFeNiTi High Entropy Alloy // Sandeep Khadka.
Author:	Khadka, Sandeep,
Description:	1 electronic resource (150 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-03, Section: B.
Contained By:	Dissertations Abstracts International86-03B.
Subject:	Mechanical engineering. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31556656
ISBN:	9798384074373

An Experimental Investigation: Microstructure and Mechanical Properties of Directed Energy Deposited AlCuFeNiTi High Entropy Alloy /
Khadka, Sandeep,

An Experimental Investigation: Microstructure and Mechanical Properties of Directed Energy Deposited AlCuFeNiTi High Entropy Alloy /Sandeep Khadka. - 1 electronic resource (150 pages)

Source: Dissertations Abstracts International, Volume: 86-03, Section: B.

High entropy alloys (HEAs) have recently emerged as a promising area in materials science and engineering, exploiting a vast compositional space through alloying. HEAs are typically defined as alloys containing five or more principal elements, each within a 5-35% compositional range. The surge in HEA research is driven by their remarkable properties and wide-ranging potential applications. Recently, additive manufacturing (AM) of HEAs has garnered significant attention, necessitating an in-depth exploration of additively manufactured HEAs. This proposed research aims to deepen our understanding of additively manufactured (AMed) HEAs by analyzing the variations introduced by the AM process and their effects on the alloy's mechanical properties. Specifically, this study focuses on the relationship between microstructure, crystallography, and nanoscale mechanical properties of HEAs. For this purpose, an AlCuFeNiTi HEA is manufactured for the first time using the directed energy deposition (DED) method with pre-alloyed powder. Various microscopic techniques, including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM), nanoindentation, and atomic force microscopy (AFM), are employed to achieve the research objectives. The microstructure of the AlCuFeNiTi HEA reveals three distinct regions resulting from local elemental composition variations, which directly impact the alloy's mechanical properties. The alloy is identified as multiphase, predominantly featuring an ordered Heusler structure (L21) and a small quantity of FCC structure with traces of C14 Laves. Additionally, needle-like and spherical Cu-rich precipitates are observed within the dendrites. During solidification, dendritic fragmentation occurs, leading to the formation of mostly equiaxed grains, as opposed to the columnar grains typically seen in other additively manufactured HEAs. Nanoindentation results indicate high hardness in the dendritic regions, while the inter-dendritic regions exhibit a softer, continuous zone. The dispersed Laves phase is identified as the strongest region, reinforcing the grain boundaries both inside and as small-size grains in the region. The hardness map obtained from indentations closely mirrors the alloy's microstructure. The study highlights the synthesis of an equiaxed HEA with multiple distinct regions influencing its overall mechanical properties. Additionally, the deformation characteristics of individual phases present in the DED AlCuFeNiTi HEA are explored through nanoindentation experiments. The effective properties of the samples are studied to understand the impact of the indentation size effect (ISE) and to determine the mechanical properties of the sample free from grain and phase boundary effects. By employing nanoindentation, this study investigates the strengthening mechanisms in the AlCuFeNiTi HEA and quantifies the strengthening factor. The study also examines the effects of laser process parameters and post-heat treatment on the microstructure and mechanical properties of the AlCuFeNiTi HEA. It is well-known that AM process parameters and subsequent post-processing heat treatments significantly impact the microstructure and mechanical properties of alloys. This research delves into these aspects to understand the effects of AM process parameters and post-process heat treatment comprehensively. Given that the DED AlCuFeNiTi HEA is manufactured for the first time, thorough exploration is crucial for a deeper understanding of these domains. Overall, this research provides an in-depth exploration of the emerging field of AMed HEAs, paving the way for more intricate research in complex high entropy alloy systems. While nanoindentation is widely used to characterize material properties, there remains a challenge in converting nanoindentation load-displacement curves into stress-strain curves due to the absence of a standardized approach. Despite various attempts to address this issue, a more accurate model for extracting mechanical properties from these curves is still needed. This study proposes an improved inverse model to determine the elastic modulus, yield strength, and hardening exponent using a single load-displacement curve. Though the model is in its beta phase, its effectiveness is demonstrated by its application to ascertain individual phase stress-strain properties of the DED AlCuFeNiTi HEA. Additionally, ongoing research on the atomic-scale tribological properties of the AlCuFeNiTi HEA using atomic force microscopy (AFM) is discussed. The study explores the sample's friction and wear properties, presenting preliminary experimental processes and results.

English

ISBN: 9798384074373Subjects--Topical Terms:

649730
Mechanical engineering.
Subjects--Index Terms:

Additive manufacturing

An Experimental Investigation: Microstructure and Mechanical Properties of Directed Energy Deposited AlCuFeNiTi High Entropy Alloy /
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500 $a Advisors: Yuya, Philip A. Committee members: Achuthan, Ajit; Mastorakos, Ioannis; Aidun, Daryush; Colak, Arzu.
502 $b Ph.D. $c Clarkson University $d 2024.
520 $a High entropy alloys (HEAs) have recently emerged as a promising area in materials science and engineering, exploiting a vast compositional space through alloying. HEAs are typically defined as alloys containing five or more principal elements, each within a 5-35% compositional range. The surge in HEA research is driven by their remarkable properties and wide-ranging potential applications. Recently, additive manufacturing (AM) of HEAs has garnered significant attention, necessitating an in-depth exploration of additively manufactured HEAs. This proposed research aims to deepen our understanding of additively manufactured (AMed) HEAs by analyzing the variations introduced by the AM process and their effects on the alloy's mechanical properties. Specifically, this study focuses on the relationship between microstructure, crystallography, and nanoscale mechanical properties of HEAs. For this purpose, an AlCuFeNiTi HEA is manufactured for the first time using the directed energy deposition (DED) method with pre-alloyed powder. Various microscopic techniques, including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM), nanoindentation, and atomic force microscopy (AFM), are employed to achieve the research objectives. The microstructure of the AlCuFeNiTi HEA reveals three distinct regions resulting from local elemental composition variations, which directly impact the alloy's mechanical properties. The alloy is identified as multiphase, predominantly featuring an ordered Heusler structure (L21) and a small quantity of FCC structure with traces of C14 Laves. Additionally, needle-like and spherical Cu-rich precipitates are observed within the dendrites. During solidification, dendritic fragmentation occurs, leading to the formation of mostly equiaxed grains, as opposed to the columnar grains typically seen in other additively manufactured HEAs. Nanoindentation results indicate high hardness in the dendritic regions, while the inter-dendritic regions exhibit a softer, continuous zone. The dispersed Laves phase is identified as the strongest region, reinforcing the grain boundaries both inside and as small-size grains in the region. The hardness map obtained from indentations closely mirrors the alloy's microstructure. The study highlights the synthesis of an equiaxed HEA with multiple distinct regions influencing its overall mechanical properties. Additionally, the deformation characteristics of individual phases present in the DED AlCuFeNiTi HEA are explored through nanoindentation experiments. The effective properties of the samples are studied to understand the impact of the indentation size effect (ISE) and to determine the mechanical properties of the sample free from grain and phase boundary effects. By employing nanoindentation, this study investigates the strengthening mechanisms in the AlCuFeNiTi HEA and quantifies the strengthening factor. The study also examines the effects of laser process parameters and post-heat treatment on the microstructure and mechanical properties of the AlCuFeNiTi HEA. It is well-known that AM process parameters and subsequent post-processing heat treatments significantly impact the microstructure and mechanical properties of alloys. This research delves into these aspects to understand the effects of AM process parameters and post-process heat treatment comprehensively. Given that the DED AlCuFeNiTi HEA is manufactured for the first time, thorough exploration is crucial for a deeper understanding of these domains. Overall, this research provides an in-depth exploration of the emerging field of AMed HEAs, paving the way for more intricate research in complex high entropy alloy systems. While nanoindentation is widely used to characterize material properties, there remains a challenge in converting nanoindentation load-displacement curves into stress-strain curves due to the absence of a standardized approach. Despite various attempts to address this issue, a more accurate model for extracting mechanical properties from these curves is still needed. This study proposes an improved inverse model to determine the elastic modulus, yield strength, and hardening exponent using a single load-displacement curve. Though the model is in its beta phase, its effectiveness is demonstrated by its application to ascertain individual phase stress-strain properties of the DED AlCuFeNiTi HEA. Additionally, ongoing research on the atomic-scale tribological properties of the AlCuFeNiTi HEA using atomic force microscopy (AFM) is discussed. The study explores the sample's friction and wear properties, presenting preliminary experimental processes and results.
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650 4 $a Materials science. $3 543314
650 4 $a Industrial engineering. $3 526216
650 4 $a Inorganic chemistry. $3 3173556
650 4 $a Nanoscience. $3 587832
653 $a Additive manufacturing
653 $a Equiaxed grains
653 $a High entropy alloys
653 $a Laves phase
653 $a Atomic force microscopy
653 $a Nanoindentation
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690 $a 0794
690 $a 0565
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710 2 $a Clarkson University. $b Mechanical Engineering. $e degree granting institution. $3 3823847
720 1 $a Yuya, Philip A. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-03B.
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791 $a Ph.D.
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