Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1968, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Arts, The Ohio State University, 1910, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

MS, University of Cincinnati, 2024, Engineering and Applied Science: Materials Science

Aluminum alloys have been heavily studied through research and extensively used in the manufacturing industry for decades. To enhance its properties, aluminum has been alloyed with several elements. This study focuses on the design and characterization of ternary and quaternary Al-rich alloys with minor additions of iron, nickel, and cobalt. In this study, aluminum alloys Al-2Fe-1Co, Al-2Ni-1Co, and Al-2Fe-2Ni-1Co (all compositions in weight percent) were investigated with a focus on the microstructural evolution and changes in hardness with respect to composition and aging. Computational analyses of the alloys were first carried out using Thermo-Calc, a software package based on the Calculation of Phase Diagrams (CALPHAD) methodology, to predict the phase equilibria in these systems. Subsequently, experimental studies were performed to verify predictions from computational analysis. First, pure aluminum, iron, nickel, and cobalt were measured to a sum of 30 g for each of the alloy compositions under consideration. The weighed elemental mixtures were homogeneously arc melted, using the vacuum arc melting (VAM) technique. The three as-cast aluminum alloys were then cut into samples of 25 pieces each. One as-cast piece from each alloy was mounted, polished and examined. First the microhardness tests were performed using a Vickers microhardness tester, and then the microstructural analysis was conducted using a scanning electron microscope, equipped with a back-scattered electron detector and an energy dispersive X-ray spectrometer, and an X-ray diffractometer. The remaining samples were aged by heat treating at 300 and 400?C each and held for 1 hour, 2 hours, 4 hours, 8 hours, 16 hours, 24 hours (1 day), 2 days, 4 days, 8 days, 16 days, 30 days, and 60 days respectively. The microstructure, hardness values, and thermal stability were then examined. The graphs were plotted to compare the hardness values with respect to aging thereby predicting thermal sta (open full item for complete abstract)

Committee: Dinc Erdeniz Ph.D. (Committee Chair); Matthew Steiner Ph.D. (Committee Member); Eric Payton Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2024, Materials Science and Engineering

The transportation sector is responsible for a significant contribution of global carbon emissions. Recent efforts to reduce carbon emissions have been focused on reducing the weight of all types of vehicles to improve efficiency. Aluminum alloys are widely used due to a combination of low density and excellent mechanical and corrosion properties. However, aluminum alloys contain high embodied emissions due to the energy intensive refinement process from bauxite ore. Recycled aluminum, called secondary aluminum, only requires around 5% of the energy needed to produce aluminum from bauxite ore (primary aluminum). Current recycling practices result in significant amounts of elemental impurities in secondary aluminum alloys, significantly decreasing their mechanical properties and limiting their uses in the transportation industry. The control of impurities during solidification ultimately controls the achievable mechanical properties of casting alloys, which are the most widely used. Thermodynamic calculations using the CALPHAD (calculation of phase diagrams) method were used to predict the effect of common impurities during solidification of secondary aluminum alloys. CALPHAD was also used to predict the effect of potential modifying elements. Lab-scale casting experiments were performed to evaluate the thermodynamic predictions via microstructure observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) techniques. Control methods for favorable microstructures were developed. From the results, a secondary structural alloy composition was chosen for production-scale experiments using high pressure die casting (HPDC). The results showed that Al-Si based alloys with Fe impurity can be effectively modified by Mn and Sr additions, and the effects of Mg and Cu impurities can be mitigated by Ce additions, leading to property improvements. The investigations also showed novel Al-Ce based alloys can (open full item for complete abstract)

Committee: Alan Luo (Advisor); Glenn Daehn (Committee Member); Jenifer Locke (Committee Member) Subjects: Materials Science

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Materials Science

As super-saturated solid solutions of Al-Mg, 5XXX series aluminum alloys are susceptible to sensitization via intergranular precipitation of the anodic ß-phase, which promotes intergranular corrosion, exfoliation and stress corrosion cracking under environmental conditions. This deleterious process occurs at time and temperature scales that eventually impact most structural applications over the course of multiple decades. Efforts to better control sensitization in these alloys, or establish predictive models, have historically been hampered by the large inter-lot variations found between nominally identical material produced by different suppliers, as the starting microstructure and total rolling reduction are not adequately specified by current cold-rolled plate tempers. The work in this dissertation demonstrates that the sensitization response of these alloys can be approached as a combination of two independent contributions: the geometric configuration of grain boundaries passing through the microstructure that are most prone to sensitization, and the rate that these boundaries sensitize due to the formation of the ß-phase. The sensitization rate kinetics of the most susceptible boundaries can be modeled using a modified Johnson-Mehl-Avarami-Kolmogorov (JMAK) theory based approach, as applied to the impinging locally sensitized regions surrounding discrete ß-phase precipitates. The microstructural configuration manifests as a sample-dependent linear scaling factor in the sensitization response. The JMAK model describes the kinetics of sensitization with excellent accuracy across all data available in the literature. This work demonstrates through the JMAK sensitization model that a clear change in the ß-phase nucleation and growth kinetics in these alloys can be observed above 100°C, and the kinetic constants both above and below that temperature can be accurately fitted. The results of the model importantly imply that sensitization at environmental temp (open full item for complete abstract)

Committee: Matthew Steiner Ph.D. (Committee Chair); Sarah Watzman Ph.D. (Committee Member); Ashley Paz y Puente Ph.D. (Committee Member); Dinc Erdeniz Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2023, Materials Science and Engineering

Rising concerns related to fuel consumption and greenhouse emissions are being addressed by the automotive industry through vehicle lightweighting. Hence to meet the stringent requirements for lightweighting, conventional steel body parts are being replaced with Al alloys, Mg alloys and composite materials. However, the use of dissimilar materials together poses a serious threat of galvanic corrosion leading to accelerated degradation of galvanically coupled body parts. Aiming to develop the automotive closure panels using carbon fiber reinforced plastics (CFRP) inner and an outer aluminum alloy sheet to replace what is now an all-steel design, corrosion studies are performed to determine effective qualification of materials. In the first part of this project, CFRP materials of two types, named as twill and random, coupled with aluminum alloys (AA) 6111 and 6022 in all combinations, are subjected to a Ford laboratory accelerated cyclic corrosion test (CETP: 00.00-L-467) and on-road testing with the help of OSU campus buses for a year. The ability of the laboratory accelerated test to predict the on-road corrosion behavior is assessed by comparing the material volume loss determined using optical profilometer, microscopic images of corroded regions, and measurements of galvanic currents of the coupons exposed to the cyclic test. Analysis of the test results indicated that the coupon combination AA6111 and CFRP-random exhibits the highest corrosion susceptibility whereas AA6022 coupled with CFRP-twill is least susceptible to galvanic corrosion among the combinations used in this study. In the second part of the study, electrochemical behavioral differences between CFRP-twill and -random contributing to the differences in activities when coupled to AA6xxx are evaluated. For this, a copper deposition technique was developed to quantify the extent of electrochemical activity and identify the exact location of electrochemically active sites on the CFRP. Optimization (open full item for complete abstract)

Committee: Gerald S. Frankel Dr. (Advisor); Narasi Sridhar Dr. (Committee Member); Jenifer Locke Dr. (Committee Member) Subjects: Atmosphere; Conservation; Energy; Engineering; Materials Science; Sustainability; Transportation

Master of Science, The Ohio State University, 2022, Materials Science and Engineering

Residential gas-fired absorption heat pumps offer a reduction in carbon dioxide emissions and energy used for space and water heating, but price constraints due to weight and cost of the system have limited mass utilization in the US. Replacement of the heavy and expensive low carbon steel evaporator with a lighter aluminum alloy evaporator would reduce the cost and weight of the novel Stone Mountain Technologies Inc. ammonia-water heat pump. The weight reduction would result in significant cost savings for shipping and installation. This research investigated the corrosive effect of 28-30 wt% ammonium hydroxide solution on aluminum alloys and the effectiveness of coatings and corrosion inhibitors through mass loss and electrochemical tests. Because this solution represented a more aggressive condition than what is found within the heat pump, in-situ testing of bare aluminum alloys was also conducted. AA6063, AA6061, AA5052, AA3003, and a proprietary Al alloy were chosen as the bare alloys to study through mass loss and electrochemical testing. Chromate conversion, zinc phosphate conversion, and sulfuric acid anodization were chosen for the coatings and benzotriazole and MEA-benzoate were chosen as the vapor phase corrosion inhibitors for testing. A year target corrosion rate of 0.0017 in/yr was established to evaluate the performance of the bare alloys, coatings, and inhibitors. Sixty-day mass loss testing resulted in breakdown and loss of protection by the three coatings and pitting for the bare alloys, especially AA3003 and AA6063. Optical microscopy, scanning electron microscopy (SEM), and optical profilometry were used to examine corrosion attack for mass loss samples. Linear polarization resistance and potentiodynamic polarization resistance conducted within four hours resulted in AA5052, chromate coated AA5052, sulfuric acid anodized AA5052, and sulfuric acid anodized AA6063 meeting the year target corrosion rate. The coated samples were eliminated from consi (open full item for complete abstract)

Committee: Gerald Frankel (Advisor); Jenifer Locke (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2021, Materials Science and Engineering

Alloying additions are employed in magnesium (Mg) to increase its corrosion performance, formability, and strength. Widely used commercial alloys such as the AZ series use Aluminum (Al) and Zinc (Zn) as the main alloying elements. The alloys used in this research contained 3, 6, or 9 wt. % Al with around 1 wt. % Zn in each alloy. This alloy system has been characterized as showing second phases forming at grain boundaries and interdendritic regions. Heterogeneities in the microstructure can vary the electrochemical potentials of the material, making them instrumental in understanding the corrosion behavior of this alloy system. From microstructural investigation, an increase in Al content increased the volume fraction and segregation of secondary phase, β. This change in microstructure showed a clear difference in corrosion morphology among alloys. Mg and its alloys form Mg oxide films in ambient conditions and Mg hydroxide in aqueous conditions. Studies have shown an inhibiting effect when Mg is in the presence of atmospheric carbon dioxide (CO2). An increase in Al content has shown to have a positive effect on corrosion performance of Mg alloys. In laboratory conditions, most tests are done in bulk solution which can limit the access of CO2 at the surface of the alloy. A simple immersion experiment was conducted to demonstrate the effect that experimental set up can have on corrosion behavior. The amount of CO2 available at the surface of the alloy is changed by varying solution height. It was shown that the interfacial pH attained a high value due to the overwhelming effect of hydrogen evolution, while the bulk solution remained buffered by the CO2. The effect of CO2 on Mg alloys was studied by testing various AZ series alloys in the presence and absence of CO2. This study aimed to identify a possible interaction between Al content and CO2 that affects the corrosion rate. Electrochemical testing was done using electrochemical impedance spectroscopy (EIS) to und (open full item for complete abstract)

Committee: Rudolph Buchheit (Advisor); Gerald Frankel (Advisor); Christopher Taylor (Committee Member) Subjects: Materials Science

Master of Science, Miami University, 2021, Mechanical and Manufacturing Engineering

Aluminum alloys 2024-T4 and 7075-T6 were joined by Friction Stir Welding (FSW) under active PID temperature control in similar-alloy welds. Positron Annihilation Lifetime Spectroscopy (PALS) and other characterization techniques were used to quantify the effects of temperature control. Three temperature setpoints were used, including an uncontrolled trial. Precipitation-hardened aluminum is strongly affected by heat-treatment temperature, so controlling the weld temperature will control the precipitation mechanisms in and around the weld. PALS profiles show a hardness map of the weld profile, which correlates to a temperature profile from the numerical model. Ultimately, precipitation can be indirectly determined through the correlation of these profiles and is confirmed through tensile testing. Statistical analysis did not show the significance of temperature control over the length of the weld, but significant variation was shown over different temperature trials. Finally, temperature control can be used in FSW to tailor weld properties to a desired application, but more testing and experimentation is necessary to fully utilize this technique.

Committee: Carter Hamilton Dr. (Advisor); Giancarlo Corti Dr. (Committee Member); Fazeel Khan Dr. (Committee Member) Subjects: Aerospace Materials; Materials Science; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2020, Materials Science and Engineering

Traditionally, the design and eventual casting of engineering components has been plagued by the assumption of homogeneous mechanical properties across the whole of the casting. Such an assumption is rarely the case and often leads to overdesign and excessive downstream waste. To combat this, the Integrated Computation Materials Engineering (ICME) approach was implemented to provide an increased level of accuracy for the prediction of location specific properties in cast aluminum. Variable properties often result from variable cooling rates that occur in a structure resulting from cooling lines or chill blocks located within the mold package, variable alloying content and finally the defects present in the alloy. In the context of this research, variable cooling was studied using the concept of a maximum chill scenario where the heat transfer coefficient (HTC) was examined and found to develop over time. The resulting microstructure was included an extremely refined eutectic silicon within the interdendritic regions. Unique, time-dependent HTC maps were created for optimized maximum chill scenario casting conditions to provide unique cooling and solidification conditions across the whole of a casting. The effect of Magnesium on hypoeutectic Al-Si alloys Primary Dendrite Arm Spacing (PDAS) was examined next. Directional solidification experimentation was coupled with Cellular Automaton (CA) simulations to develop a model to predict the location specific PDAS within Al-Si-Mg alloys. Additionally, location specific properties are known to result from defects within the microstructure such oxide inclusions and porosity. These voided regions act as regions of increased stress and result in premature failure of engineered components. In this work the fluid flow, filling conditions and free surface of the molten aluminum was examined to create a new model that was accurately shown to predict the location specific defect content in a cast structure. Finally, the sum of thi (open full item for complete abstract)

Committee: Alan Luo (Advisor); Glenn Daehn (Committee Member); Stephen Niezgoda (Committee Member) Subjects: Engineering; Materials Science

Master of Science (M.S.), University of Dayton, 2019, Mechanical Engineering

Experimental study accomplished the characterization of fatigue crack growth rates and mechanisms in both hand and die forged Aluminum 7085-T7452. Testing was conducted at various positive and negative loading ratios, primarily focused on L-S and T-S orientations to discover a correlation between crack tip branching or turning mechanisms and stress intensity. Interior delaminations were found to originate in the interior of the specimen and propagate outward to the surface and manifested as splitting cracks parallel to the loading direction. Stress intensity ranges have been correlated with the onset of crack deviation from the primary crack plane, as well as, the transition to branching dominated fatigue crack growth.

Committee: David Myszka (Committee Chair); James Joo (Committee Member); Thomas Spradlin (Committee Member); Mark James (Committee Member) Subjects: Aerospace Materials; Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2019, Materials Science and Engineering

Metal-rich primers have been used for corrosion protection on metals for over 40 years. Recently, researchers started to investigate the use of metal-rich primers on aluminum alloys as an alternative to hexavalent-chromate systems because of their good corrosion-protective properties. The active aluminum-rich primer (AlRP) was invented and developed at NAVAIR (Patuxent River, MD) to protect aluminum alloys and steels. The Al alloy (Al-Zn-In) pigments in AlRP were fabricated from a sacrificial anode alloy, which has a lower open circuit potential (OCP) than common aluminum alloys. However, initial results indicated that the pigment particles in AlRP tended to undergo severe self-corrosion. Therefore, the Al pigments are pretreated in a trivalent chromium passivation (TCP) bath to reduce the self-corrosion rate. The objectives of this study are to understand the corrosion protection properties of AlRP on aluminum alloy 2024-T3 substrate and to evaluate the effect of TCP treatment on the Al pigment particles. The polarization curves of AA2024-T3 and the active aluminum alloy (Al-Zn-In) show that TCP-treated active aluminum alloy has a lower corrosion potential than AA2024-T3 and thus would cathodically protect it. AlRP-coated samples were exposed in accelerated exposure tests, GMW14872 and B117. Exposed samples were then examined using scanning electron microscopy and energy dispersive X-ray spectroscopy to understand the coating degradation process. In addition, samples were immersed in 0.1M NaCl solution for an extended time and were monitored using electrochemical impedance spectroscopy. The AlRP with TCP-treated pigments out performs the coating with untreated pigments. The TCP treatment on the Al-Zn-In pigments was evaluated. The chemistry and morphology of Al pigment particles treated in a TCP bath for three different immersion times were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and ener (open full item for complete abstract)

Committee: Gerald Frankel (Advisor); Jenifer Locke (Committee Member); Narasi Sridhar (Committee Member) Subjects: Materials Science

Master of Science, Miami University, 2019, Mechanical and Manufacturing Engineering

Aluminum alloys 2024-T3 and 7075-T6 were joined by friction stir welding using bobbin and conventional tools types. The effectiveness of placing each alloy on the advancing and retreating side within the bobbin and conventional tool configurations was investigated, and comparisons were made between the welds of the two tool types. Microstructural imaging, micro-hardness mapping, tensile testing, and computational modeling were used to evaluate the weld quality of each tool and material configuration. Temperature data and simulation profiles indicated that the temperature distribution from both tools favored the advancing side with the bobbin tool reaching higher temperatures than the conventional tool. Higher mechanical properties were reported for conventional tool welds than those performed with the bobbin tool, and material placement affected the weld performance in the conventional tool configurations. All tensile specimens fractured on the 2024 side of the weld and specimens joined with the conventional tool were more consistent than those with the bobbin tool. Differential scanning calorimetry identified the precipitation behavior of the alloys which correlated well to the mechanical properties of the welds. Optical microscopy and EBSD analysis highlighted advanced stirring patterns through the weld thickness. Identical equiaxed grain structures observed in the stir zone of both alloys suggested complete recrystallization.

Committee: Carter Hamilton Ph.D (Advisor); Giancarlo Corti Ph.D (Committee Member); Fazeel Khan Ph.D (Committee Member) Subjects: Materials Science; Mechanical Engineering

Master of Science (MS), Ohio University, 2019, Mechanical Engineering (Engineering and Technology)

Aluminum alloys with improved electrical and mechanical performance are a highly sought-after due to their potential use as energy efficient conductors in power transmission, electronics, and aerospace systems. In this thesis, a novel hot extrusion alloying (HEA) process was used to synthesize aluminum/graphite nano-alloys using commercially available AA1100 and graphite nanoparticles (GNP) as precursors to improve electrical properties. The effects of GNP content from 0 – 1 wt.%, on the electrical and mechanical properties were evaluated. Results showed that the addition of 0.25 wt.% GNPs to the Al substrate improved its electrical conductivity by 2.1%, current density by 7.9%, ultimate tensile strength by 6.1% and yield strength by 30.3% compared to the control sample with no GNP additives. Improvements in electrical conductivity and current density were observed for all Al/GNP formulation at 60 °C and 90 °C. Ductility of the Al/GNP nano-alloys decreased with increasing GNP content. The improvement in Al/GNP electrical performance is attributed to GNP exfoliation at the temperatures and shear stresses experienced during hot extrusion, leading to the formation of highly conductive graphene particles.

Committee: Keerti Kappagantula (Advisor) Subjects: Materials Science; Mechanical Engineering

Doctor of Engineering, Cleveland State University, 2017, Washkewicz College of Engineering

This dissertation explores the role of different types of convection on macrosegregation and on dendritic array morphology of two aluminum alloys directionally solidified through cylindrical graphite molds having both cross-section decrease and increase. Al- 19 wt. % Cu and Al-7 wt. % Si alloys were directionally solidified at two growth speed of 10 and 29.1 µm s-1 and examined for longitudinal and radial macrosegregation, and for primary dendrite spacing and dendrite trunk diameter. Directional solidification of these alloys through constant cross-section showed clustering of primary dendrites and parabolic-shaped radial macrosegregation profile, indicative of “steepling convection” in the mushy-zone. The degree of radial macrosegregation increased with decreased growth speed. The Al- 19 wt. % Cu samples, grown under similar conditions as Al-7 wt. % Si, showed more radial macrosegregation because of more intense “stepling convection” caused by their one order of magnitude larger coefficient of solutal expansion. Positive macrosegregation right before, followed by negative macrosegregation right after an abrupt cross-section decrease (from 9.5 mm diameter to 3.2 mm diameter), were observed in both alloys; this is because of the combined effect of thermosolutal convection and area-change-driven shrinkage flow in the contraction region. The degree of macrosegregation was found to be higher in the Al- 19 wt. % Cu samples. Strong area-change-driven shrinkage flow changes the parabolic-shape radial macrosegregation in the larger diameter section before contraction to “S-shaped” profile. But in the smaller diameter section after the contraction very low degree of radial macrosegregation was found. The samples solidified through an abrupt cross-section increase (from 3.2 mm diameter to 9.5 mm diameter) showed negative macrosegregation right after the cross-section increase on the expansion platform. During the transition to steady-state after the expansion, radia (open full item for complete abstract)

Committee: Surendra Tewari Ph.D. (Advisor); Jorge Gatica Ph.D. (Committee Member); Orhan Talu Ph.D. (Committee Member); Rolf Lustig Ph.D. (Committee Member); Kiril Streletzky Ph.D. (Committee Member) Subjects: Aerospace Materials; Automotive Materials; Chemical Engineering; Condensed Matter Physics; Engineering; Fluid Dynamics; High Temperature Physics; Materials Science; Metallurgy

Master of Sciences (Engineering), Case Western Reserve University, 2017, Materials Science and Engineering

The focus of this study was on the tensile behavior and damage development in 5083- H131 Al-Mg alloy sensitized to different levels. Samples were tested in the as-received state, after sensitization at 175°C for 100hrs, or 80°C for >500hrs. Tensile testing was conducted under moderate (50%RH) or low (<1%RH) humidity environments to determine the environmental effects on the mechanical behavior of the material. Three different deformation/fracture modes were present depending on the sensitization level and testing environment. Interrupted tensile tests and microscopy revealed that strain was more heterogeneously distributed in the highly sensitized specimens compared to the as-received ones. Differential scanning calorimetry was also performed as a means of determining the degree of sensitization of specimens thermally exposed at temperatures from 60-175°C. This technique was able to detect the presence of Mg-rich phase(s) at thermal exposures as low as 60°C, though it has quantitative limits due to the resolution limit.

Committee: John Lewandowski Dr. (Advisor); David Schwam Dr. (Committee Member); Clare Rimnac Dr. (Committee Member) Subjects: Materials Science; Mechanical Engineering