Atomistic simulations of crystalline defect interactions in metallic alloys
department or school: Applied Science, Faculty of
department or school: Materials Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Umashankar, Hariharan
issued: 2025-06-17T00:13:02Z
issued: 2025
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Atomistic events govern processes at the microstructural length scale that ultimately affect macroscopic material behavior. For instance, solute segregation to internal interfaces such as grain boundaries (GB) can significantly affect the mechanical properties. Similarly, vacancy interactions with GBs and the diffusion along the GBs are also important phenomena that control the microstructure evolution. Experimental investigations of such processes are laborious, time-consuming, and present technical challenges. This study deals with a computational approach to model solute segregation and vacancy interactions at the atomistic scale using two different simulation methods. The first method uses Density Functional Theory (DFT) calculations to quantify the solute-GB interactions in a BCC Ti- 25 at.% Mo alloy. Electrons are considered explicitly in DFT, serving as a state-of-the-art method for segregation phenomena. A major challenge in studying alloys is the multitude of atomic arrangements of the host species. Results from solutes - Y, Zr and Nb occupying all sites in the alloy yield a spectrum of solution energies. Taking the example of the strongest segregating solute, Yttrium, segregation and solution energies at GBs and in the bulk are calculated across three compositions of Mo - 25, 50 and 75 at.% allowing trends to be mapped for the full composition space. The second approach uses a surrogate model, such as the Atomic Cluster Expansion. Initially, a workflow is established using the training data from Embedded Atom Method (EAM) calculations. Here, properties of bulk, fifteen different <100> symmetric tilt GBs in pure Pt and Au, bulk mixing enthalpies of Pt-Au alloys and vacancy formation energies in bulk Pt-Au alloys are studied. The DFT data for some structures that are chosen based on the EAM surrogate modeling are generated to build a regression model with “ab-initio” accuracy. A property of interest, such as vacancy formation energy in ~ 50 at. % Au for bulk…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/91364
note: Atomistic simulations of crystalline defect interactionsin metallic alloysbyHariharan UmashankarB.Tech., Indian Institute of Technology (IIT) Madras, 2018M.Tech., Indian Institute of Technology (IIT) Madras, 2018A THESIS SUBMITTED IN PARTIAL FULFILLMENTOF THE REQUIREMENTS FOR THE DEGREE OFDoctor of PhilosophyinTHE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES(Materials Engineering)THE UNIVERSITY OF BRITISH COLUMBIA(Vancouver)June 2025© Hariharan Umashankar, 2025The following individuals certify that they have read, and recommend to the Faculty of Grad-uate and Postdoctoral Studies for acceptance, the dissertation entitled:Atomistic simulations of crystalline defect interactions in metallic alloyssubmitted byHariharan Umashankar in partial fulfillment of the requirements for the degreeof Doctor of Philosophy in Materials EngineeringExamining Committee:Matthias Militzer, Professor, Materials Engineering, UBCSupervisorChadwick Sinclair, Professor, Materials Engineering, UBCSupervisory Committee MemberJoerg Rottler, Professor, Physics and Astronomy, UBCSupervisory Committee MemberRoman Krems, Professor, Chemistry, UBCUniversity ExaminerMauricio Ponga de la Torre, Associate Professor, Mechanical Engineering, UBCUniversity ExaminerChuang Deng, Professor, Mechanical Engineering, University of ManitobaExternal ExamineriiAbstractAtomistic events govern processes at the microstructural length scale that ultimately affectmacroscopic material behavior. For instance, solute segregation to internal interfaces such asgrain boundaries (GBs) can significantly affect the mechanical properties. Similarly, vacancyinteractions with GBs and the diffusion along the GBs are also important phenomena thatcontrol the microstructure evolution. Experimental investigations of such processes are labori-ous, time-consuming, and present technical challenges. This study deals with a computationalapproach to model solute segregation and vacancy interactions at the atomistic scale using twodifferent si…
has type: Thesis/Dissertation
date issued: 2025-11
is shown at: 10.14288/1.0449126
language: eng
degree discipline: Materials Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Militzer, Matthias
type: Text
identifier URI: http://hdl.handle.net/2429/91364