Date of Award

2019

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering (PhD)

Administrative Home Department

Department of Materials Science and Engineering

Advisor 1

Gregory Odegard

Advisor 2

Paul Sanders

Committee Member 1

Stephen Hackney

Committee Member 2

S Gowtham

Abstract

High electrical conductivity Al-Zn-TM (TM=Transition metals) alloys with improved mechanical properties and thermal resistance are developed with an integrated computational material engineering (ICME) strategy. From a series of ab initio density functional theory (DFT) simulations assessing combinations of ternary alloys, Al-Zn-Ni and Al-Zn-Zr are determined as alloys with relatively high electrical conductivity compared to several other ternary Al alloy combinations. The zero-temperature stable structure of precipitates formed in these alloys are determined from computed enthalpy of formation as L12, with particular focus of examining the influence of Zn on stabilizing the desired L12 precipitate phase.

Scanning transmission electron microscopy (STEM) is used to examine the role of Zn addition on the morphology and phase transformation of precipitates formed in the alloys. Elemental mapping and energy-dispersive X-ray spectroscopy (EDX) in STEM mode demonstrate the enrichment of Zn, Zr and Ni in the precipitate phases. Moreover, mechanical and electrical properties of the alloys are determined. The results indicate that Zn addition improves microhardness and strength but reduces electrical conductivity, creep and thermal resistance of Al-Zr and Al-Ni alloys. Zn also has the potential to enhance the ductility of Al-Zr alloy by increasing work hardening through reduction of the alloy stacking fault energy.

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