Doctoral Dissertations

Abstract

"The objective of the current work was to fabricate a crack-free functionally graded Ti6Al4V and Inconel 625 thin wall structure by Laser Metal Deposition (LMD). One potential application for the current material system is the ability to fabricate a functionally graded alloy that can be used in a space heat exchanger. The two alloys, Inconel 625 and Ti6Al4V are currently used for aerospace applications. They were chosen as candidates for grading because functionally grading those combines the properties of high strength/weight ratio of Ti6Al4V and high temperature oxidation resistance of Inconel 625 into one multifunctional material for the end application. However, there were challenges associated with the presence of Ni-Ti intermetallic phases (IMPs). The study focused on several critical areas such as (1) understanding microstructural evolution, (2) reducing macroscopic cracking, and (3) reducing mixing between graded layers. Finite element analysis (FEA) was performed to understand the effect of process conditions on multilayer claddings for simplified material systems such as SS316L and Inconel 625 where complex microstructures did not form. The thermo-mechanical models were developed using Abaqus™ (and some of them experimentally verified) to predict temperature-gradients; remelt layer depths and residual stresses. Microstructure evolution along the functionally graded Ti6Al4V and Inconel 625 was studied under different processing and grading conditions. Thermodynamic modeling using Factsage (v 6.1) was used to construct phase diagrams and predict the possible equilibrium major/minor phases (verified experimentally by XRD) that may be present along the functionally graded Ti6Al4V and Inconel 625 thin wall structures"--Abstract, page iii.

Advisor(s)

Newkirk, Joseph William

Committee Member(s)

Liou, Frank W.
Kohser, Ronald A.
Zhou, Caizhi
Van Aken, David C.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Sponsor(s)

Air Force Research Laboratory (Wright-Patterson Air Force Base, Ohio)
Missouri University of Science and Technology. Intelligent Systems Center

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2014

Pagination

x, 207 pages

Note about bibliography

Includes bibliographical references (pages 198-206).

Rights

© 2014 Syamala Rani Pulugurtha, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Library of Congress Subject Headings

Pulsed laser deposition
Heat resistant alloys
Thermodynamics

Thesis Number

T 10537

Electronic OCLC #

894223139

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