Matching Items (7)

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Market and Feasibility Study for Novel Processing of Aluminum Alloy for Applications in 3D Printing

Description

One of the more difficult portions of our capstone project has been identifying a potential market for our Clay Metal—whether there even is a potential market. To that end, I

One of the more difficult portions of our capstone project has been identifying a potential market for our Clay Metal—whether there even is a potential market. To that end, I plan to use the strategies discussed in MSE482 to complete a feasibility study and market analysis for our two clay metal systems to determine if our alloys are viable as a product in any market and to determine what steps we might need to take to bring our material to that market. While we have done some preliminary research similar to a feasibility study, a more comprehensive understanding of our problem and its existing solutions will help us optimize our design with respect to desirable properties and cost. There are various metrics used to identify what materials properties are most desirable for consumers; the exact metric we use will become clearer when I have identified our demographic.

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Date Created
  • 2017-05

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Microstructural Evolution and Corrosion Behavior of Chromium Coated Aluminum 7075

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Surface Mechanical Attrition Treatment (SMAT) is a process used to coat metallic alloy surfaces with a nanocrystallized layer via mechanical abrasion. SMAT has garnered a significant amount of interest from

Surface Mechanical Attrition Treatment (SMAT) is a process used to coat metallic alloy surfaces with a nanocrystallized layer via mechanical abrasion. SMAT has garnered a significant amount of interest from the scientific community as a surface treatment technique due to the ability of this fine grain top layer to provide several benefits to its constituent alloy, namely significantly higher hardness, fatigue strength, and most pertinently, greatly improved corrosion resistance. Emerging research suggests that SMAT can also be used to apply powder coatings onto target substrates. A given substrate can be installed in a ball mill, where stainless steel balls coated with pure elemental powder deliver sustained impact onto the substrate, embedding the powders onto its surface. This paper will explore the process of coating aluminum 7075 coating with chromium powder via SMAT, and the effects doing so will have on the corrosion resistance properties of the aluminum 7075. Traditionally, high-strength alloys have been treated with chromium via the process of electroplating, where the alloys are subjected to a hexavalent chromium plating procedure that is known to risk releasing toxic carcinogens into the environment. Coating these alloys with SMAT could minimize such negative externalities, while yielding benefits unique to the SMAT coating process itself. Baseline corrosion testing reveals that the corrosion resistance properties of the aluminum 7075 improved marginally when exposed to SMAT without the addition of any chromium powder. A literature review conducted in this paper of select studies on SMAT coating also demonstrates that material properties intrinsic to aluminum 7075 and pure chromium powder, as well as interaction effects occurring between aluminum and chromium when subjected to mechanical alloying, could enable the SMAT coating of aluminum 7075 with chromium to result in greatly enhanced corrosion resistance properties. While this was not accomplished within the duration of the Honors Project due to logistical difficulties brought forth by the COVID-19 epidemic, the baseline corrosion testing performed, as well as the literature review of studies directly relevant to the matter, should hopefully provide some information of value in any future exploration of the topic.

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Date Created
  • 2020-05

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Ionic Liquid Corrosion of Magnesium-Aluminum Alloys

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In 2015, the United States consumed about 140.43 billion gallons of gasoline, resulting in the emission of over 1 billion metric tons of carbon dioxide, according to the U.S. Energy

In 2015, the United States consumed about 140.43 billion gallons of gasoline, resulting in the emission of over 1 billion metric tons of carbon dioxide, according to the U.S. Energy Information Administration. Despite continued efforts to develop more efficient engines and cleaner fuels, a major barrier to reducing energy consumption and CO2 production is the mass of the vehicle. Replacing traditional automotive materials such as iron and steel with lighter-weight materials is a big step toward improving fuel economy. Magnesium has great potential for use in the automotive industry because of its low density, about 78% less than the density of steel, and high strength-to-weight ratio. Using cast magnesium instead of steel can reduce the overall weight of a vehicle, improving performance and increasing fuel efficiency. However, magnesium’s high susceptibility to corrosion limits its feasibility as a substitute for traditional materials.

This project aimed to understand the effects of composition and phase distribution on the corrosion behavior of magnesium-aluminum (Mg-Al) alloys in an ionic liquid electrolyte. The purpose of studying corrosion in nonaqueous ILs is to determine the anodic dissolution behaviors of the alloy phases without the interference of side reactions that occur in aqueous electrolytes, such as di-oxygen or water reduction. Three commercial Mg-Al alloys were studied: AZ91D (9% Al), AM60 (6% Al), and AZ31B (3% Al). An annealed alloy containing solid-solution α-phase Mg-Al with 5 at% aluminum content (Mg5Al) was also used. The ionic liquid chosen for this project was 1:2 molar ratio choline-chloride:urea (cc-urea), a deep eutectic solvent. After potentiostatic corrosion in cc-urea, the magnesium alloys were found to form a high surface area porous morphology as corrosion duration increased. This morphology consists of aluminum-rich ridges formed by Al nanowires surrounding an aluminum-poor base area, but with an overall increase in surface Al composition, indicating selective dealloying of the Mg in cc-urea and redistribution of the Al on the surface. Further work will focus on the development of hydrophobic coatings using ionic liquids.

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Date Created
  • 2016-05

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Corrosion and corrosion-fatigue behavior of 7075 aluminum alloys studied by in situ X-ray tomography

Description

7XXX Aluminum alloys have high strength to weight ratio and low cost. They are used in many critical structural applications including automotive and aerospace components. These applications frequently subject the

7XXX Aluminum alloys have high strength to weight ratio and low cost. They are used in many critical structural applications including automotive and aerospace components. These applications frequently subject the alloys to static and cyclic loading in service. Additionally, the alloys are often subjected to aggressive corrosive environments such as saltwater spray. These chemical and mechanical exposures have been known to cause premature failure in critical applications. Hence, the microstructural behavior of the alloys under combined chemical attack and mechanical loading must be characterized further. Most studies to date have analyzed the microstructure of the 7XXX alloys using two dimensional (2D) techniques. While 2D studies yield valuable insights about the properties of the alloys, they do not provide sufficiently accurate results because the microstructure is three dimensional and hence its response to external stimuli is also three dimensional (3D). Relevant features of the alloys include the grains, subgrains, intermetallic inclusion particles, and intermetallic precipitate particles. The effects of microstructural features on corrosion pitting and corrosion fatigue of aluminum alloys has primarily been studied using 2D techniques such as scanning electron microscopy (SEM) surface analysis along with post-mortem SEM fracture surface analysis to estimate the corrosion pit size and fatigue crack initiation site. These studies often limited the corrosion-fatigue testing to samples in air or specialized solutions, because samples tested in NaCl solution typically have fracture surfaces covered in corrosion product. Recent technological advancements allow observation of the microstructure, corrosion and crack behavior of aluminum alloys in solution in three dimensions over time (4D). In situ synchrotron X-Ray microtomography was used to analyze the corrosion and cracking behavior of the alloy in four dimensions to elucidate crack initiation at corrosion pits for samples of multiple aging conditions and impurity concentrations. Additionally, chemical reactions between the 3.5 wt% NaCl solution and the crack surfaces were quantified by observing the evolution of hydrogen bubbles from the crack. The effects of the impurity particles and age-hardening particles on the corrosion and fatigue properties were examined in 4D.

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Date Created
  • 2017

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Characterization of the Dynamic Strength of Aluminium at Extreme Strain Rates and Pressures

Description

The study of response of various materials to intense dynamic loading events,

such as shock loading due to high-velocity impacts, is extremely important in a wide

variety of military and industrial applications.

The study of response of various materials to intense dynamic loading events,

such as shock loading due to high-velocity impacts, is extremely important in a wide

variety of military and industrial applications. Shock loading triggers extreme states,

leading to high pressures and strain rates, and neglecting strength is a typical

approximation under such conditions. However, recent results have shown that strength

effects are larger than expected, so they must be taken into account. Recently,

hydrodynamic instabilities, the most common being the Rayleigh-Taylor (RTI) and

Richtmyer-Meshkov (RMI) instabilities, have been used to infer the dynamic strength of

materials at high pressure conditions. In our experiments and simulations, a novel RMI

approach is used, in which periodic surface perturbations are made on high purity

aluminium target, which was laser ablated to create a rippled shock front. Due to the

slow linear growth rate of RMI, the evolution of the perturbations on the back surface of

the sample as a result of the rippled shock can be measured via Transient Imaging

Displacement Interferometry (TIDI). The velocity history at the free surface was

recorded by spatially resolved laser velocimetry. These measurements were compared

with the results from the simulations, which were implemented using rate independent

and rate dependent material models, to characterize the dynamic strength of the

material. Simulations using the elastic-perfectly plastic model, which is rate

independent, failed to provide a value of dynamic yield strength that would match

experimental measurements of perturbation amplitudes. The Preston-Tonks-Wallace

(PTW) model, which is rate dependent model, worked well for aluminium. This model

was, in turn, used as a reference for calibrating the rate dependent Steinberg-Lund

model and the results from simulations using the calibration models were also compared

to experimental measurements.

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Date Created
  • 2017

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Understanding plasticity and fracture in aluminum alloys and their composites by 3D X-ray synchrotron tomography and microdiffraction

Description

Aluminum alloys and their composites are attractive materials for applications requiring high strength-to-weight ratios and reasonable cost. Many of these applications, such as those in the aerospace industry, undergo fatigue

Aluminum alloys and their composites are attractive materials for applications requiring high strength-to-weight ratios and reasonable cost. Many of these applications, such as those in the aerospace industry, undergo fatigue loading. An understanding of the microstructural damage that occurs in these materials is critical in assessing their fatigue resistance. Two distinct experimental studies were performed to further the understanding of fatigue damage mechanisms in aluminum alloys and their composites, specifically fracture and plasticity. Fatigue resistance of metal matrix composites (MMCs) depends on many aspects of composite microstructure. Fatigue crack growth behavior is particularly dependent on the reinforcement characteristics and matrix microstructure. The goal of this work was to obtain a fundamental understanding of fatigue crack growth behavior in SiC particle-reinforced 2080 Al alloy composites. In situ X-ray synchrotron tomography was performed on two samples at low (R=0.1) and at high (R=0.6) R-ratios. The resulting reconstructed images were used to obtain three-dimensional (3D) rendering of the particles and fatigue crack. Behaviors of the particles and crack, as well as their interaction, were analyzed and quantified. Four-dimensional (4D) visual representations were constructed to aid in the overall understanding of damage evolution. During fatigue crack growth in ductile materials, a plastic zone is created in the region surrounding the crack tip. Knowledge of the plastic zone is important for the understanding of fatigue crack formation as well as subsequent growth behavior. The goal of this work was to quantify the 3D size and shape of the plastic zone in 7075 Al alloys. X-ray synchrotron tomography and Laue microdiffraction were used to non-destructively characterize the volume surrounding a fatigue crack tip. The precise 3D crack profile was segmented from the reconstructed tomography data. Depth-resolved Laue patterns were obtained using differential-aperture X-ray structural microscopy (DAXM), from which peak-broadening characteristics were quantified. Plasticity, as determined by the broadening of diffracted peaks, was mapped in 3D. Two-dimensional (2D) maps of plasticity were directly compared to the corresponding tomography slices. A 3D representation of the plastic zone surrounding the fatigue crack was generated by superimposing the mapped plasticity on the 3D crack profile.

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Created

Date Created
  • 2014

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Parity violation in the hadronic weak interaction

Description

This thesis deals with the first measurements done with a cold neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The experimental technique consisted of capturing polarized

This thesis deals with the first measurements done with a cold neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The experimental technique consisted of capturing polarized cold neutrons by nuclei to measure parity-violation in the angular distribution of the gamma rays following neutron capture. The measurements presented here for the nuclei Chlorine ( 35Cl) and Aluminum ( 27Al ) are part of a program with the ultimate goal of measuring the asymmetry in the angular distribution of gamma rays emitted in the capture of neutrons on protons, with a precision better than 10-8, in order to extract the weak hadronic coupling constant due to pion exchange interaction with isospin change equal with one ( hπ 1). Based on theoretical calculations asymmetry in the angular distribution of the gamma rays from neutron capture on protons has an estimated size of 5·10-8. This implies that the Al parity violation asymmetry and its uncertainty have to be known with a precision smaller than 4·10-8. The proton target is liquid Hydrogen (H2) contained in an Aluminum vessel. Results are presented for parity violation and parity-conserving asymmetries in Chlorine and Aluminum. The systematic and statistical uncertainties in the calculation of the parity-violating and parity-conserving asymmetries are discussed.

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Date Created
  • 2012