Date of Award
2025-07-01
Degree Name
Master of Science
Department
Physics
Advisor(s)
Jorge Munoz
Abstract
High-throughput first-principles calculations of point defects are emerging as a powerful tool to accelerate materials discovery in applications [1]. Substitutional, antisite, and vacancy defects can play an important role in the mechanical and thermal properties of intermetallic alloys [2]. In this present work I compute the thermal and mechanical properties of shape-memory alloy nickel-titaniun (NiTi) in the B19â?? martensitic and B2 austenitic phases from molecular dynamics (MD), using a second nearest neighbor (2NN) modified embedded atom method (MEAM) [3] classical potential in the temperature range from 200K to 600K and composition range from 45 atomic percent to 55 atomic percent nickel. We developed and used a python framework to generate input files, run the simulations, and analyze the data, which we call Utilities To Execute Pipelines (UTEP). Thirty-nine lattice parameters and five temperatures were simulated for eleven distinct compositions around equiatomicity, for antisite defects each with three distinct defect concentrations on 16,000-atom supercells, meanwhile for vacancy defects each with three distinct defect concentrations, for a total of 45,045 MD simulations of 2000 time steps each with a time step size of 5 fs. We extracted temperature-dependent materials parameters from fits to the internal energies by fitting the Birch-Murnaghan equation of state. Thermodynamic properties such as the vibrational entropy were obtained using two different approaches from the materials parameters the first one was using the Moruzzi-Janak-Schwarz [4] approximation and secondly from the integration de of the density of states and the Bose-Einstein statics [5]. Finally, the configurational entropy due to the defects was obtained from the Warren-Cowley parameters up to fourth nearest neighbors [6,7]. Defects are energetically unfavorable, but can become thermodynamically stabilized at high temperature, particularly on the nickel-rich side. The bulk modulus decreases with temperature in the nickel-rich side, while the opposite is observed on the titanium-rich side.
Language
en
Provenance
Received from ProQuest
Copyright Date
2025-07
File Size
121 p.
File Format
application/pdf
Rights Holder
Diego Armando Juarez Rosales
Recommended Citation
Juarez Rosales, Diego Armando, "Advanced Study Of Nickel-Titanium Alloy: Effects Of Point Defects On Mechanical And Thermodynamic Properties" (2025). Open Access Theses & Dissertations. 4393.
https://scholarworks.utep.edu/open_etd/4393