Dissertations / Theses: 'Aluminum alloys Bauschinger effect'

1

Jordon, James Brian. "DAMAGE AND STRESS STATE INFLUENCE ON BAUSCHINGER EFFECT IN ALUMINUM ALLOYS." MSSTATE, 2006. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04172006-133053/.

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In this work, the Bauschinger effect is shown to be intimately tied not only to plasticity but to damage as well. The plasticity-damage effect on the Bauschinger effect is demonstrated by employing different definitions (Bauschinger Stress Parameter, Bauschinger Effect Parameter, the Ratio of Forward-to-Reverse Yield, and the Ratio of Kinematic-to-Isotropic Hardening) for two differently processed aluminum alloys (rolled and cast) in which specimens were tested to different prestrain levels under tension and compression. Damage progression from second phase particles and inclusions that were generally equiaxed for the cast A356-T6 aluminum alloy and elongated for the rolled 7075 aluminum alloy was quantified from interrupted experiments. Observations showed that the Bauschinger effect had larger values for compression prestrains when compared to tension. The Bauschinger effect was also found to be a function of damage to particles/inclusions, dislocation/particle interaction, the work hardening rate, and the Bauschinger effect definition.

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2

Boger, Richard Keith. "Non-monotonic strain hardening and its constitutive representation." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1138979144.

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3

Fielding, S. E. "Fatigue and the Bauschinger effect in ferritic alloys." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304216.

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4

Gan, Wei. "Precipitation and strengthening in AL-GE-SI alloys." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1135275701.

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5

Eaton, James Allen. "Effect of temperature and percent cold work on the mechanical properties of aluminum alloy 3104." Master's thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03302010-020243/.

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6

Khosla, Maya. "The effect of moisture exposure on pretreated aluminum alloys." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80060.

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Changes in pretreated 5182, 6061 and 7075 aluminum surfaces on exposure to moisture for short times was studied. The pretreatment used was the standard ASTM method for FPL etching of aluminum. The moisture treatment used was either immersion in water at 81° C or exposure to water vapor at 81° C. The experimental techniques used to analyze the pretreated aluminum surfaces before and after exposure to moisture were ESCA or XPS, AES, high resolution SEM, and specular reflectance FTIR. There was a change in the surface topography on exposure of the aluminum surfaces to water as determined using high resolution SEM. Stoichiometric calculations based on XPS analysis were made to estimate the amount of excess water present on the surface. Water was present on the surface before exposure to moisture, for all three alloys. The amount of water present on the surface was found to decrease with increasing times of exposure to water for all three alloys. This result was consistent with the model that pseudoboehmite formed on the surface was being converted into boehmite at longer times of exposure to water. The thickness of the oxide layer was found to increase with time of exposure to water based on ESCA results. The same conclusion was reached by depth profiling the oxide layer using AES. The rate of increase in the concentration of pseudoboehmite on the surfaces as calculated from FTIR data went in the order 7075 < 5182 < 6061. The activation energy for the third step (transport of soluble species to the surface) in the conversion of surface Al₂O₃ to AlOOH was calculated from FTIR results to be 3.5 kcal mol⁻¹.
Master of Science

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7

Laurent, Michel P. "A continuum surface layer effect in polycrystalline aggregates." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06082009-170819/.

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8

Sarkar, Jaydeep. "Characterisation of yield stress anisotropy and the Bauschinger effect in alloys and composites : an application of neutron diffraction." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624289.

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9

Golbahar, Behnam. "Effect of grain refiner-modifier interaction on the performance of A356.2 alloy." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2008. http://theses.uqac.ca.

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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2008.
La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en ingénierie. CaQQUQ Comprend des réf. bibliogr. (f. 149-155). Publié aussi en version électronique. CaQQUQ

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10

Shang, Lihong. "Effect of microalloying on microstructure and hot working behavior for AZ31 based magnesium alloy." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115880.

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The formability of Mg alloy sheet in the as-hot rolled condition depends on the microstructure developed during hot rolling. In general, the formability of Mg alloys is improved by finer grain sizes. 'Microalloying' levels of calcium (Ca), strontium (Sr), and cerium (Ce) have been found to refine the as-cast structure, but there is no information as to whether this effect will be reflected in the as-hot worked structure and formability. Thus, in this work, the effects of microalloying levels of calcium (Ca), strontium (Sr), and cerium (Ce) on the microstructures (from as-cast to as-hot rolled) and subsequent hot deformation behavior of AZ31, nominally 3% Al, 1% Zn, and 0.3%Mn, were systematically investigated.
To include the effect of solidification rate these alloys were cast in different moulds (preheated steel mould, Cu-mould, and water cooled Cu-mould). One-hit compression testing at temperatures between 250°C ∼ 400 °C, strain rates of 0.001, 0.01, 0.1 s-1 and strains from 0.2 up to 1.0, was performed to investigate the basic hot compression behavior, while two-hit compression testing was conducted to determine the static softening behavior. Hot rolling of the microalloyed AZ31 alloys was then carried out to study the effects of microalloying on as-hot rolled structure under two sets of rolling schedules. To investigate the formability of these microalloyed sheets, tensile tests were completed over a temperature range between ambient and 450°C, at strain rates between 0.1 and 0.0003 s-1.
Results show that Ca and Sr act to refine the as cast grain size and the second phases, consistently promoting fine and uniform as-hot rolled grain structure. With regard to grain refinement, calcium has the strongest effect, whereas Ce is most effective for second phase refinement. In addition, microalloying retards grain growth during hot tensile testing. Multiple alloying presents a combined and complementary effect.
A refined and uniform grain structure combined with well dispersed and thermally stable second phases significantly improves the hot formability of AZ31 sheets by promoting dynamic recrystallization (DRX) in the matrix, resisting grain coarsening, and retarding the development of cavitation and necking. Under the superplastic condition of 450°C and 0.0003 s -1, the elongation was improved by 17% with Ca only, 26% with Ca and Ce, 51% with Ca and Sr, and 59% with Ca, Sr and Ce.

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11

Hsu, Emilie Chia Ching 1979. "Effect of deformation conditions on texture and microstructure of magnesium sheet AZ31." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99768.

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Magnesium alloys have a great potential in automotive industries, compared to steel and aluminium (Al), Magnesium (Mg) is much lighter and this weight reduction improves fuel efficiency and lowers green gas emission. Due to its hexagonal crystal structure, magnesium has poor ductility at room temperature. Magnesium's ductility improves significantly above about 200°C due to thermal activation of additional slip systems. This has lead to efforts to form auto-body panels with commercial AZ31 magnesium sheet at elevated temperatures. In this work, various AZ31 magnesium alloy materials were used to investigate the influence of deformation conditions on texture and microstructure. Moreover, it is to define the correlation between formability and different deformation mechanisms.
It was observed that only basal slip and twinning contributed to room temperature deformation. As deformation temperature increased, an increase in ductility in Mg contributed to dynamic recrystallization occurring readily at elevated temperatures (≥300°C). Even coarse grain material experienced significant tensile elongation due grain refinement. Depending on temperature and strain rate, different deformation mechanisms were activated and lead to different failure modes (moderate necking, cavity, strong necking). More specifically, deformation at elevated temperature in the low-strain-rate regime with stress exponent n about 2-3 and activation energy close to grain-boundary diffusion of Mg (Q = 92 kJ/mol) is characteristic of GBS. Deformation at elevated temperature in the high strain rate regime showed that the stress exponent increased to a value close to 5 and that the activation energy was consistent with the one for Mg self-diffusion (135 kJ/mol) and for diffusion of Al in Mg (143 kJ/mol). This was indicative of a dislocation creep deformation mechanism. Plus the six-fold symmetric patterns of the {1 100} and {1120} pole figures and the splitting of basal plane distribution are another indication of slip mechanism or of dislocation creep mechanism.
The optimum deformation behavior for AZ31 sheet was found to be for the material with fine grain microstructure. The highest elongation of 265% was obtained with the material having initial grain size of 8 mum. In addition, strain-rate sensitivity, which is a good indication of material's ductility, also was the highest in material with 8 mum grain size. As a common trend, the strain-rate sensitivity increased with decreasing strain rate, increasing temperature and decreasing grain size.
In terms of drawability of AZ31 sheet, the deformation controlled by GBS resulted in a fair drawability/formability property with r-value about 1 whereas a deformation mechanism controlled by dislocation creep showed a good drawability with r-value above 1.5. Due to activation of additional slip systems (non-basal and ), the thinning of the sheet was prevented, in particular at deformation conditions of 450°C with 0.1s-1 where r-value was highest. This deformation condition might suggest good forming process parameters, especially for deep drawing, for the commercial AZ31 sheet under investigation. A preliminary study of Forming Limit Diagram for AZ31 sheet was performed by the Limit Dome Height test method at 300°C. The FLD0 of AZ31 was found to be 67%; the part depth of biaxial forming was 1.86 in; and the maximum LDH varied from 2.4 to 2.6 in.

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12

Deshpande, Jayesh U. "The effect of mechanical mold vibration on the characteristics of aluminum alloys." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-092106-151830/.

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13

Klinter, Andreas. "Wetting behaviour of aluminum alloys on ceramic substrates and its effect on the stability of aluminum foams." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92344.

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14

Kubiak, Angela Dawne. "Effect of homogenization on high temperature deformation behaviour of AA3xxx aluminum alloys." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7382.

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The effect of homogenization practice and alloy Mn content on the dispersoid density and high temperature constitutive behaviour of AA3xxx aluminum alloys has been studied. Experimental work was conducted on three as-cast alloys with different Mn compositions: AA3102 (0.26 wt% Mn), an intermediate Mn alloy (0.75 wt% Mn), and AA3003 (1.27 wt% Mn). Homogenization treatments were conducted at soak temperatures from 500 to 630°C and times of 1 to 24 hours. The evolution of microstructure during homogenization (at 600°C over a soak time of 24 hours) was characterized using electrical conductivity measurements and optical microscopy. Electrical conductivity measurements were used to estimate the variation of Mn in solid solution during homogenization. Qualitative observations of constituent particle morphology and dispersoid precipitation/dissolution were made. Compression tests were conducted using a Gleeble 3500 thermomechanical simulator at strain rates (0.1 to 10s-1) and deformation temperatures (300 to 600°C) experienced during the industrial extrusion of AA3xxx alloys. Yield stress, flow stress, and work hardening results were obtained from the compression tests and a physically-based constitutive model was employed to describe the results. The model was used to quantify the effect of homogenization practice and alloy Mn content on constitutive behaviour. Homogenized microstructure observations were combined with model results to determine the effect of dispersoid density on constitutive behaviour. Extrusion trials were performed on Rio Tinto Alcan’s state-of-the-art research extrusion press located at the Alcan Research and Development Center in Jonquiere, Quebec. AA3102 and AA3003 alloys were extruded in as-cast and homogenized conditions at temperatures of 400 and 500°C. Extrusion pressure results were used to develop a relationship between extrusion pressure and flow stress.

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15

Ozdemir, Ozgur. "Effect of strontium on the oxidation behavior of molten aluminum-magnesium alloys." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102689.

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Magnesium additions to aluminum enhance strength and hardness, lowering density, and improve corrosion resistance. However, during melting and casting processes, significant amounts of magnesium are lost due to selective oxidation. Preventing these losses would reduce the production cost and improve the quality of the final product.
The effects of various levels of strontium addition on the oxidation behaviour of aluminum-magnesium alloy melts were investigated by monitoring sample weight gains with time using a thermogravimetric balance at 750°C. Sample cross-sections have been examined in detail using Hitachi S-4700 Field Emission Gun Scanning Electron Microscope, and phases formed on the oxide layer and in the alloy morphology were identified by EDS, WDS and low angle X-ray diffraction techniques. It was observed that in the absence of Sr, the Al-Mg samples gained substantial amounts of weight by formation of spinel (MgAl2O4) phase at the oxide-metal interface. Samples containing Sr had significantly lower weight gains. The drop in total weight gain by Sr additions was about 98% in low Mg-containing Al-Mg alloys. This change in oxidation behavior was linked to the presence of a Sr-enriched liquid phase underneath the first formed MgO layer, suppressing the formation of spinel crystals. In addition, spherical equilibrium shapes are found in the different as-cast and oxidized alloys of Al-Mg-Sr.

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16

Crepeau, Paul Noles. "The effect of processing and microstructure on the mechanical properties of aluminum alloy 339-T5." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/20193.

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17

Rivero, Paz Ive. "The effect of key microstructure features on the machining of an aluminum-silicon casting alloy /." View online, 2010. http://ecommons.txstate.edu/engttad/1.

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18

Balasundaram, Arunkumar. "Effect of stress state and strain on particle cracking damage evolution in 5086 wrought al-alloy." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14809.

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19

El, Sebaie Ossama. "L'effet de l'addition du "mischmetal", du taux de refroidissement et du traitement thermique sur la microstructure et la dureté des alliages Al-Si de type 319, 356, et 413 = Effect of mischmetal, cooling rate and heat treatment on the microstructure and hardness of 319, 3456, and 413 Al-Si alloys /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.

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20

Ammar, Hany. "Effet des imperfections de la coulée sur les propriétés en fatigue des alliages de fonderie aluminium silicium = Effect of casting imperfections on the fatigue properties of aluminum-silicon casting alloys /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.

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21

Giles, Tanya L. "The effect of friction stir processing on the microstructure and mechanical properties of AF/C458 aluminum lithium alloy." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FGiles.pdf.

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22

Cho, Jaeshin. "Effect of microstructure of aluminum alloys on the electromigration-limited reliability of VLSI interconnects." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13636.

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23

Tash, Mahmoud. "Effect [sic] des paramètres métallurgiques sur le comportement d'usinage des alliages 356 et 319 (étude de forage et de taraudage) /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.

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24

Gomes, Affonseca Netto Nelson. "The Effect of Friction Stir Processing on The Microstructure and Tensile Behavior of Aluminum Alloys." UNF Digital Commons, 2018. https://digitalcommons.unf.edu/etd/790.

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Friction Stir Processing (FSP) is a promising thermomechanical technique that is used to modify the microstructure of metals locally, and thereby locally improve mechanical properties of the material. FSP uses a simple and inexpensive tool, and has been shown to eliminate pores and also reduce the sizes of intermetallics in aluminum alloys. This is of great interest for research on solidification, production and performance of aluminum alloy castings because FSP can enhance the structural quality of aluminum casting significantly by minimizing the effect of those structural defects. In the literature, there is evidence that the effectiveness of FSP can change with tool wear of the tool used. Therefore, a study was first conducted to determine the effect of FSP time on the tool life and wear in 6061-T6 extrusions. Results showed the presence of two distinct phases in the tool life and wear. Metallographic analyses confirmed that wear in Phase I was due to fracture of the threads of the tool and Phase II was due to regular wear, mostly without fracture. Moreover, built-up layers of aluminum were observed between threads. The microhardness profile was found to be different from those reported in the literature for 6061-T6, with Vickers hardness increasing continuously from the the stir zone to the base material. To investigate the degree of effectiveness of FSP in improving the structural quality of cast A356 alloys, ingots with different quality (high and low) were friction strir processed with single and multiple passes. Analysis of tensile test results and work hardening characteristics showed that for the high quality ingot, a single pass was sufficient to eliminate the structural defects. Subsequent FSP passes had no effect on the work hardening characteristics. In contrast, tensile results and work hardening characteristics improved with every pass for the low quality ingot, indicating that the effectiveness of FSP was dependent on the initial quality of the metal. The evolution of microstructure, specifically the size and spacing of Silicon (Si) eutectic particles, was investigated after friction stir processing of high quality A356 castings with single and multiple passes. Si particles were found to coarsen with each pass, which was in contrast with previous findings in the literature. The nearest neighbor distance of Si particles also increased with each FSP pass, indicating that microstructure became progressively more homogeneous after each pass. In the literature, the improvement observed after FSP of Al-Si cast alloys was attributed to the refinement of Si particles. Tensile data from high quality A356 ingot showed that there was no correlation between the size of Si particles and ductility. To the author’s knowledge, this is the first time that the absence of a correlation between Si particle size and ductility has been found.

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25

Agarwal, Himanshu. "Effect of loading condition, stress state and strain on three-dimensional damage evolution in 6061 wrought Al-alloy." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14798.

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26

Conlon, Kelly Timothy. "The effect of mesoscopic spatial heterogeneity on the plastic deformation of Al-Cu alloys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/NQ42838.pdf.

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27

Anderson, Danny. "Effect of the joint addition of aluminum and molybdenum on the precipitation and recrystallization in HSLA steels." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66207.

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28

Spence, Timothy. "The Effect of Machining Residual Stresses on the Dimensional Stability of Aluminum Alloys used in Optical Systems." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/104.

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Dimensional stability of materials is of critical importance in the fabrication of precision components used for applications such as optical systems. One source of dimensional instability is residual stress produced on the surfaces of parts due to machining operations. A creep model is proposed in this research that describes how these stressed layers affect the overall geometry of a component as they creep over time and temperature. Depth corrected XRD stress measurements and a bimetallic strip model were utilized to quantify the residual stress layer of two machining operations. The creep model parameters were determined by monitoring curvature over time and temperature. This model can be used for two purposes, the prediction of long term storage effects on part geometry for purposes of reliability assessment, and the design of short term, moderate temperature stress relief treatments. Two alloys were investigated, aluminum 6061-T6, and aluminum 4032-0. A methodology for applying the observed creep strain to complex parts using a finite element analysis is proposed.

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29

Todoroff, Peter Kent. "Effect of Turbulence on the Passive Film Growth and Associated Durability of Aluminum Alloys in Simulated Seawater." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83770.

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Turbulent fluid flow at high Reynolds numbers presents significant degradation risks to active-passive metals due to enhanced localized degradation phenomena. A multidisciplinary experiment was proposed to study the relationship between hydrodynamics in fully-developed pipe flow and both the growth and performance characteristics of passive films. Preliminary work was performed to set up (i) an environmental chamber for the experiment, (ii) design a custom wall shear stress sensor and constant temperature anemometer traverse system to monitor hydrodynamic conditions in-situ, (iii) monitor in-situ degradation through an array of ultrasonic thickness transducers, and (iv) acquire data and control the environment via a LabVIEW routine. A validation experiment was conducted on a 1220 mm long experimental section of 45.7 mm inner diameter AA2024-T3 tubing in simulated seawater. Extensive degradation was observed in-situ and confirmed with ex-situ techniques after sequential exposure to fully-developed turbulent flow at an expected wall shear stress of 10 Pa for 180ks (Reynolds number of 122,000) and then at 40 Pa for 630ks (Reynolds number of 262,000). No typical erosion-corrosion hydrological features were observed, however significant pitting and intergranular corrosion were observed with corrosion product caps covering 47% of the total ultrasonic transducers' measurement area. Passive film and pit growth were recorded via ultrasonic thickness measurements with an observed simultaneous decrease in dissolved oxygen content. The validation experiment successfully demonstrated the capability of the designed and constructed sensors for the proposed experiment. Numerous areas of suggested development and research were identified to ensure accuracy and improve interpretation of future experiments.
Master of Science

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30

Enin-Okut, Edu Owominekaje. "The effect of alumina coatings on the oxidation behavior of nickel-base alloys." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/20226.

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31

Li, Jinxia. "THE EFFECT OF MICROSTRUCTURE AND TEXTURE ON HIGH CYCLE FATIGUE PROPERTIES OF AL ALLOYS." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/522.

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High cycle fatigue tests were carried out on a medium strength continuous casting AA 5754 Al alloy, and new generation high strength AA 2026 and AA 2099 Al alloys. The effect of texture on fatigue properties and short crack behavior were studied. The strengthening mechanisms were also thoroughly investigated for the two high strength alloys.Texture played an important role in the anisotropy of fatigue strength for the AA 5754 Al alloy. Being a solution strengthened alloy, it had a fatigue strength of 120% σy. High strength Al alloys had a strong tendency for planar slip due to the high density of coherent and shearable precipitates in the alloys. Texture was a key factor controlling the crack initiation and propagation. The crack path and the possible minimum twist angles were measured using EBSD and calculated theoretically by a crystallographic model. Based on the micro-texture measured by EBSD, the crack paths were predicted for the AA 2099 alloy and confirmed by the observed values.The excellent balance of superior fatigue properties and high tensile strength of AA 2026 and AA 2099 was attributed to the reduced population of Fe-containing particles, homogeneously distributed precipitates and dislocations. The addition of Zr coupled with the optimized thermo-mechanical treatment strongly restrained the recrystallization, refined the grain structure and promoted the homogenization of the precipitates. Moreover, the retainment of the deformation texture developed during the hot extrusion provided significant orientation strengthening in the high strength Al alloys.Fatigue cracks tended to initiate at coarse second phase particles on sample surfaces and the crack population varied markedly with the applied stresses in the high strength Al alloys. The relationship between of the crack population and the applied stress level was studied and quantified by a Weibull distribution function. Since the measured cracknumbers were associated with the crack initiate sites (i.e., the weakest links) in an alloy, the fatigue weakest-link density, which is defined as the crack population per unit area when stress close to the ultimate tensile stress, and the weakest-link strength distribution can all be calculated and regarded as a property of the studied materials.

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32

Sutton, Scott Christopher. "Characterization and Modeling of Lightweight Alloys in the Warm Forming Regime." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524129785253984.

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33

Hung, Lie-chung. "Electropolishing of Ti-6A1-4V surgical implant alloy and its effect on corrosion behavior." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/20731.

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34

Iyer, A. Vishwanath. "Effect of tool shoulder profile on the axial force and joint strength of friction stir spot welded aluminum alloys." Thesis, Wichita State University, 2012. http://hdl.handle.net/10057/5599.

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In many industries, the use of articulated robots has proven to be an efficient and beneficial way in which to reduce manufacturing costs, e.g., by increasing productivity through automating repetitive processes. However, because of their limited payload capacity, articulated robotic arms have found limited use in processes like friction stir welding (FSW), which require precise position control under relatively high process loads. This limitation in payload has restricted the use of robots to low-loading operations in manufacturing. One way to increase the usefulness of robots for FSW is to reduce the process forces to which they are required to react. One potential area of robotic application is friction stir spot welding (FSSW), a variant of FSW. FSSW is typically used to join two overlapped sheet metal workpieces. A significant portion of the process cycle of FSSW is the plunge cycle. The axial (z) load generated in the process can be substantial depending on selection of the weld tool and process parameters. This study is a continuation of the work performed in the first phase on a gantry-style FSW machine to analyze the process feedback forces, mainly the axial force. In the first phase of this project, the level of the axial force required to produce FSSW in an AA2024-T3 bare aluminum sheet, was significantly lowered by reducing the weld tool shoulder diameter from 0.4 inches (10.2 mm) to 0.3 inches (7.6 mm). Results from the second phase of this project included the influence of three weld tool shoulder geometries, namely concave, convex scrolls, and flat scrolls, on the axial force, mechanical strength (shear strength), and macrostructural properties produced between AA7075-T6 (typical of stringers) and AA2024-T3 (typical of an aircraft skin). The effects of process parameters were analyzed using the design of experiments (DOE) approach. The results of this research suggest that basic and swept FSSW of dissimilar aerospace alloys can be successfully performed at an axial force that is suitable for robotic applications.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

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35

Meng, Qingjiang. "Effect of cu content on corrosion behavior and chromate conversion coating protection of 7xxx series al alloys." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1059574004.

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36

Elhadad, Shimaa. "Effect of trace elements on the microstructure and porosity formation in 319 type Al-Si-Cu alloys." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2003. http://theses.uqac.ca.

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37

Kim, Youngseok. "Characterizations of alloying Cu effect on electrochemical reactions of Al-Cu solid solution alloys." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143130451.

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38

Tan, Evren. "The Effect Of Hot-deformation On Mechanical Properties And Age Hardening Characteristics Of Al-mg-si Based Wrought Aluminum Alloys." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607937/index.pdf.

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Microstructural and mechanical characterizations of heat treatable Al-Mg-Si-Cu based wrought aluminum alloys have been studied. The aim of this work was to produce fine grained, high strength alloy by adjusting processing conditions: deformation, solutionizing and aging. First, primary characterization was carried out via SEM-EDS analyses and tensile tests. Then an extensive experimental study has been carried out on two sets of samples. The first set has been studied to determine the ideal conditions for solutionizing and aging processes by analyzing the variation of hardness with different solutionizing and aging time and temperature. The second set, have first been mechanically deformed by swaging at four different deformations and four different temperatures, then heat treated. The hardness measurements have been carried out before and after solutionizing and also after aging. Finally, recrystallization behavior has been investigated by measuring grain size before and after solutionizing treatment using image analyzer software. The initial characterizations showed that Mg2Si and complex iron, manganese bearing intermetallics were the primary particles observed in the &
#945
-Al matrix. Nearly 140HB hardness could be obtained with solutionizing at 530°
C and aging at 175°
C for 8 hours which was determined as the optimum treatment for obtaining peak hardness. When shaping (deformation) was concerned
strength loss was the overall outcome of any hot or cold deformation before solutionizing
which was most probably due to the destruction of the initial microstructure. Improvement in the percent elongation was the promising aspect of this application. Strength loss was increased for samples deformed at higher temperatures and higher reductions.

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39

Taylor, Ryan Chandler. "Effect of a Simulated Butterfly Valve on the Erosion-Corrosion Rate of Nickel Aluminum Bronze Alloys in Highly Turbulent Seawater." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83818.

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Nickel aluminum bronze (NAB) alloys are used in naval and maritime applications for their excellent corrosion resistance under the influence of seawater. One application involves the use of a NAB butterfly valve within a NAB fluid line to control fluid flow of seawater. Due to the chaotic environment, the corrosion rate of the NAB tubing downstream from the valve increases significantly. The disc angle at which the valve alters fluid flow causes an increase in the fluid velocity and an increase in the turbulence produced on the downstream side of the valve. These fluid conditions contribute to the increase in the corrosion rate of the NAB piping downstream from the valve. This thesis aims to characterize how the change in the disc angle of the butterfly valve causes a change in the erosion-corrosion rate of NAB downstream from the valve. A butterfly valve is simulated using orifice plates of varying diameters to mimic flow conditions at different disc angles. An orifice plate is a simple device with a hole in its center that is designed to restrict fluid flow across a fluid line. Under the same hydrodynamic conditions, the orifice produces nearly the exact same flow coefficients as the valve. At a volumetric flowrate of 0.00757 m^3/s a total of eight locations found along the liquid/metal interface produced pitting sites. The average passivation layer thickness is also measured.
Master of Science

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40

Bandi, Raghava. "Effect of Surface Treatment on the Performance of CARALL, Carbon Fiber Reinforced Aluminum Dissimilar Material Joints." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011869/.

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Fiber-metal laminates (FML) are the advanced materials that are developed to improve the high performance of lightweight structures that are rapidly becoming a superior substitute for metal structures. The reasons behind their emerging usage are the mechanical properties without a compromise in weight other than the traditional metals. The bond remains a concern. This thesis reviews the effect of pre-treatments, say heat, P2 etch and laser treatments on the substrate which modifies the surface composition/roughness to impact the bond strength. The constituents that make up the FMLs in our present study are the Aluminum 2024 alloy as the substrate and the carbon fiber prepregs are the fibers. These composite samples are manufactured in a compression molding process after each pre-treatment and are then subjected to different tests to investigate its properties in tension, compression, flexural and lap shear strength. The results indicate that heat treatment adversely affects properties of the metal and the joint while laser treatments provide the best bond and joint strength.

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41

Morano, Robert Natale. "Effect of R-ratio on crack closure in Al-Li 2090 T8E41, investigated non-destructively with x-ray microtomography." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19903.

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42

Cevik, Gul. "Investigation Of The Effect Of Orientation And Heat Treatment On The Stress Corrosion Cracking Susceptibility Of 7050 Aluminum Alloy." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12605220/index.pdf.

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In the present work, the effect of variation in specimen orientation and heat treatment on the Stress Corrosion Cracking (SCC) susceptibility of 7050 aluminum alloy was investigated in 3,5% NaCl solution and under freely corroding conditions. For this purpose, Constant Extension Rate Tests (CERT) was performed on precracked Compact Tension (CT) specimens and the Direct Current Potential Drop technique was applied to measure the crack lengths. In addition to crack length versus time curves, the relationship between the crack growth rate and the stress intensity factor was determined. Fractographic analysis was utilized extensively to support the findings related with basic mechanisms of cracking. The alloy was found to be in the most susceptible state in the SL orientation, in which the crack propagation direction is parallel to the rolling direction. The resistance to SCC is higher in the TS but at maximum in LT orientation where the loading direction is parallel to the rolling direction. In the peak aging treatment, T651, alloy is susceptible to SCC in SL orientation. When the over aging treatment, T7651, is applied the resistance is increased and the two step over aging treatment, T73651, has resulted in an additional improvement in this orientation. On the other hand, the alloy showed higher resistance to SCC in TS and LT orientations in T651 condition compared to the T7651 and T73651 treatments. In these orientations, the alloy is less susceptible in T73651 condition than in T7651 treatment.

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恵子, 名取, and Keiko Natori. "微細複合組織金属の変形機構および塑性加工性に関する研究." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12867122/?lang=0, 2014. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12867122/?lang=0.

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ヘテロ構造組織を有する鉄・非鉄金属の組織形態に注目して,微視的構造やその挙動が巨視的現象(変形特性,成形性)として発現するメカニズムを解明することを目的とした.鉄系金属ではDual Phase型高張力鋼のスプリングバック現象のひずみ速度依存性,非鉄系金属では半凝固鋳造法と強ひずみ加工を組み合わせた亜共晶アルミニウム合金の衝撃後方押出し成形性に注目した.これらの検討によりいずれの試料においても,結晶粒界よりもスケールの大きいヘテロ構造に由来した変形機構が支配的であることが明らかになった.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University

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44

Sutton, Kirk C. "An investigation of the effect of steam cleaning and aluminum oxide treatment on the wettability and surface free energy of alloys commonly used in dentistry." Thesis, The University of Texas Health Science Center at San Antonio, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10137632.

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Purpose: The purpose of this investigation was to evaluate the effect of aluminum oxide airborne particle abrasion, with and without subsequent steam cleaning on the surface free energy of alloys commonly used in dentistry, in an attempt to produce optimal surfaces for adhesion. Materials and Methods: Twelve samples, with dimensions 13 x 18 x 1 mm, of each: Type IV high noble gold alloy, metal ceramic gold-palladium high noble alloy, chrome-cobalt base metal alloy were cast and divested with glass bead airborne particle abrasion. Twelve samples, with dimensions 13 x 18 x 10 mm, of titanium alloy were milled using an Origin Proteus 5x Milling Machine. Samples were treated with 1) Steam cleaning only, 2) Aluminum oxide airborne particle abrasion and 3) Aluminum oxide airborne particle abrasion with subsequent steam cleaning. Contact angle measurements were recorded immediately after each treatment and at 1 and 12 hours, using a goniometer and the sessile drop method. Surface free energy was calculated using VCA Optima XE software.

Results: Steam cleaning treatment showed no significant changes in surface free energy (dynes/cm), compared to pretreatment values for the alloys investigated except Titanium alloy, which showed a modest increase in surface energy (p < 0.05). Aluminum oxide airborne particle abrasion and aluminum oxide airborne particle abrasion with steam cleaning, resulted in an increase in surface free energy for all alloys investigated when compared to pretreatment and steam clean only values. Steam cleaning following airborne particle abrasion produced significantly lower (p<0.001) surface free energy values compared to airborne particle abrasion alone for high noble gold alloy and metal ceramic gold-palladium high noble alloy. Exposure to ambient air following steam cleaning had minimal or non-enduring effects on surface free energy for all alloys investigated except Titanium alloy, which showed a significant decrease (p<0.001) in surface free energy with time of ambient exposure. Exposure to ambient air following airborne particle abrasion with aluminum oxide resulted in a significant decrease (p<0.001) in surface free energy for high noble gold alloy, metal ceramic gold-palladium high noble alloy and chrome-cobalt base metal alloy, however, Titanium alloy showed no ambient exposure effects. Ambient exposure following aluminum oxide airborne particle abrasion with steam cleaning resulted in a significant decrease (p<0.001) in surface free energy for all alloys investigated.

Conclusions: Within the limitations of this study, it was found that aluminum oxide airborne particle abrasion, with and without subsequent steam cleaning, significantly increased the surface free energy of the dental alloys investigated. Steam cleaning following aluminum oxide airborne particle abrasion significantly reduced the surface free energy gain that the high noble alloys experienced with aluminum oxide airborne particle abrasion alone. And finally, exposure to ambient air following aluminum oxide airborne particle abrasion with and without subsequent steam cleaning resulted in a significant decrease in surface free energy for most alloys investigated.

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White, Brad Derek. "Cathodoluminescence spectroscopy studies of aluminum gallium nitride and silicon device structures as a function of irradiation and processing." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141325302.

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46

Ghods, Masoud. "Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation." Cleveland State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu1500217305972883.

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Kovarik, Libor. "Microstructural study and modeling of metastable phases and their effect on strenghthening [sic] in Al-Mg-Cu-Si alloying system." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1149006665.

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48

Davoodi, Ali. "Mechanistic studies of localized corrosion of Al alloys by high resolution in-situ and ex-situ probing techniques." Doctoral thesis, Stockholm : Kemivetenskap, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4588.

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49

Zhemchuzhnikova, Daria. "Influence of the extreme grain size reduction on plastic deformation instability in an AlMg and AlMgScZr alloys." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0324/document.

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L'élaboration de nouveaux alliages maintient un fort intérêt pour le phénomène d’instabilité plastique, ou l'effet Portevin-Le Chatelier (PLC), provoqué par l'interaction des dislocations avec des atomes de soluté. Par ailleurs, l'effet PLC attire l'intérêt comme un exemple remarquable d'auto-organisation dans les systèmes dynamiques. Il est associé à des motifs complexes de séries de chutes de contrainte liées à la nucléation et au mouvement des bandes de déformation dans le matériau déformé, et nécessite une compréhension de l'auto-organisation des dislocations. La déformation plastique des alliages Al-Mg est sujette à l'instabilité dans une large gamme de conditions expérimentales. Pour cette raison, les alliages Al-Mg binaires ont longtemps servi d'objets modèles pour l'étude de l'effet PLC. En même temps, l'utilisation pratique des alliages binaires Al-Mg est limitée en raison d’une faible résistance mécanique. Une amélioration significative de leurs propriétés peut être atteinte en ajoutant des solutés supplémentaires, conduisant en particulier à la formation de précipités. En outre, une forte réduction de la taille de grains du polycristal pourrait être une technique clé pour produire des matériaux à haute résistance et ténacité. Cependant, il existe très peu d'information, souvent contradictoire, sur l'instabilité PLC dans les alliages Al-Mg à grains fins et contenant des précipités. Le but de l'étude de cette thèse a été d'étudier les caractéristiques spécifiques de l'effet PLC dans les alliages à base AlMg, avec et sans nanoparticules, à gros grains et à grains fins, ces derniers obtenus par une méthode de déformation plastique sévère. Grâce à l’application de méthodes d’extensométrie locale, notamment de la technique de corrélation d’images, ces études ont révélé une persistance non habituelle de la propagation des bandes de déformation dans les alliages comprenant des précipités et/ou des grains fins. Ce mode dynamique est observé dans un large intervalle de vitesses de déformation, tandis qu’il n’apparait qu’à haute vitesse dans des alliages modèles AlMg. Par ailleurs, l’analyse des distributions statistiques des amplitudes des chutes de contrainte a révélé une tendance vers une statistique en loi puissance, caractéristique du mode de propagation. Ce phénomène est attribué à une modification du couplage spatial entre les dislocations, due à la concentration de contraintes internes. La combinaison de ces études avec l’analyse de l’émission acoustique a mis en évidence une influence de la microstructure sur la compétition entre un facteur aléatoire et la synchronisation des dislocations. Enfin, l’étude par corrélation d’images a permis d’observer une interrelation entre l’instabilité PLC et la formation de la striction
The elaboration of new alloys sustains a strong interest to the phenomenon of unstable plastic flow, or the Portevin–Le Chatelier (PLC) effect, caused by interaction of dislocations with solute atoms. Moreover, this effect attracts interest as a rich example of self-organization in dynamical systems. It is associated with complex patterns of stress serrations related to nucleation and motion of deformation bands in the deforming material, and requires understanding of self-organization of dislocations. Plastic deformation of Al-Mg alloys is prone to instability in a wide range of experimental conditions. For this reason, binary Al-Mg alloys served for a long time as model objects for investigation of the PLC effect. At the same time, the practical use of binary Al-Mg alloys is limited because of their low strength. A significant improvement of their properties can be achieved by additional alloying, in particular, leading to precipitation. Further, extensive grain refinement could be a key technique used to produce tough and high- strength materials. However, there exists very limited and often contradictory information on the PLC instability in fine-grained Al-Mg alloys containing precipitates. The objective of the present thesis was to investigate specific features of the PLC effect in AlMg-based alloys with and without nanoscale particles, both in coarse-grained and fine-grained states, the latter obtained by severe plastic deformation. Using local extensometry methods, particularly the image correlation technique, these studies revealed an unusual persistence of the propagation of deformation bands in alloys with precipitates and/or fine grains. This dynamic mode is observed in a wide range of strain rates, whereas it only appears at high strain rate in model Al-Mg alloys. Moreover, the analysis of statistical distributions of stress drop amplitudes revealed a tendency to power law statistics characteristic of the propagation mode. This phenomenon was attributed to a modification of the spatial coupling between dislocations due to the concentration of internal stresses. The combination of these studies with the acoustic emission analysis uncovered an influence of the microstructure on the competition between a random factor and the dislocation synchronization. Finally, the study by the image correlation made it possible to observe an interrelation between the PLC instability and the neck formation

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Mori, Thiago José de Almeida. "Materiais e técnicas para nanoestruturas magnetoelétricas compósitas." Universidade Federal de Santa Maria, 2014. http://repositorio.ufsm.br/handle/1/3928.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Hybrid nanostructures which integrate two or more technologically interesting physical properties are fundamental for developing new generations of electronic devices. Exhibiting at least two coupled ferroic orders, multiferroics are an outstanding class of multifunctional materials. Compounds which present coupling between ferromagnetism and ferroelectricity are specially interesting. Although natural multiferroics are rarely found, the possibility of obtaining strain-mediated magnetoelectric coupling in composite structures, by integrating magnetostrictive and piezoelectric layers, paves the way to control electric properties by applying magnetic field or to the electric control of magnetism. Nevertheless, most scientific efforts have been on monophasic compounds or bulk composites. Considering the incorporation of magnetoelectric nanostructures in devices, expanding the scope of the magnetoelectric effect and targetting it to different kinds of applications is needed. Besides new characterization techniques, seeking new alternative materials to the lead-based piezoelectrics or oxide-based magnetostrictives is necessary. Recently, a few works using semiconductors such as ZnO and AlN, or amorphous magnetic alloys such as those based on Co, Fe and Ni, have been reported. In spite of not presenting remarkable piezoelectric and magnetostrictive effects, the features of such materials are promising for high frequency applications, for instance. Considering these issues, four independent surveys are presented. Firstly, the origin of the coupling, latest advances and current scenario of the field are reviewed. Then magnetostriction measurements in thin films are addressed by employing a direct technique based on the cantilever-capacitance method. The goals are to study magnetoelastic properties of some materials whose magnetostriction are not found very often in literature, and to check the reliability of this technique for investigating thin films. In this sense, measurements of some amorphous magnetic alloys mainly based on Co, Fe and Ni are performed. Most samples presents larger magnetoelastic response for magnetic field applied along the magnetization easy axis, as opposed to the theoretically expected. Two investigations on aluminum nitride thin films are reported. Firstly, the growth of AlN films onto several different substrates and buffer layers is studied. Films grown onto glass and polyimide show excellent structural properties for eletromechanical systems and flexible electronics applications. Samples with low residual stress on silicon substrates, suitable for incorporating in existing technologies, are obtained. Secondly, bilayers composed by AlN and ferromagnetic films are investigated. In addition to the structural and morphological properties of the AlN films which are checked, the magnetic characterization of the structures also contributes to design multilayers for exploring the magnetoelectric effect. Finally, problems involving electric fields in scanning probe microscopies are adressed. Surface images of AlN piezoelectric films are systematically acquired. Among other major observations, the possibility of getting reliable piezoresponse images of strongly polarized areas as well as of visualizing ferroelastic domains, is demonstrated. Furthermore, a new microscopy for investigating a sample s ferro and piezoelectric properties is proposed, exploring the direct piezoelectric effect. By utilizing acoustic excitation and electrical detection, the potency of this technique is illustrated with measurements on quartz and AlN surfaces.
Nanoestruturas híbridas, integrando duas ou mais propriedades físicas de grande interesse tecnológico, são fundamentais para o desenvolvimento de novas gerações de dispositivos eletrônicos. Uma classe interessante de materiais multifuncionais são os multiferróicos, que exibem pelo menos duas ordens ferróicas acopladas. Dentre eles, os que apresentam acoplamento entre ferromagnetismo e ferroeletricidade despertam interesse especial. Apesar de serem raros de ocorrer naturalmente, a possibilidade de gerar efeito magnetoelétrico em estruturas compósitas, intermediado pela deformação elástica entre camadas magnetostrictivas e piezoelétricas, abre caminho para que seja possível controlar propriedades elétricas aplicando-se campo magnético, ou propriedades magnéticas aplicando-se campo elétrico. Todavia, a maior parte das pesquisas atuais ainda envolve compostos monofásicos ou compósitos em forma massiva. Tendo em vista a incorporação de nanoestruturas magnetoelétricas em dispositivos, é fundamental ampliar a abrangência do efeito magnetoelétrico e direcioná-lo para diferentes tipos de aplicações. Para isto, além de novas técnicas de caracterização, é necessário buscar-se materiais alternativos aos tradicionais piezoelétricos baseados em chumbo e magnetostrictivos baseados em óxidos. Recentemente tem-se encontrado trabalhos pontuais onde são utilizados piezoelétricos semicondutores como ZnO e AlN, e ligas magnéticas amorfas como as baseadas em Co, Fe e Ni. Mesmo sem apresentar efeitos piezoelétrico e magnetostrictivo com magnitudes notáveis, as características destes materiais são promissoras para aplicações envolvendo altas frequências, por exemplo. Neste necessário, são apresentados quatro estudos independentes entre si. Primeiramente, é realizada uma revisão sobre a origem do acoplamento, os últimos avanços e o panorama atual das pesquisas na área. Em seguida, através de uma técnica direta baseada no método do cantiléver-capacitância, aborda-se o problema das medidas de magnetostricção em amostras na forma de filmes finos. Os objetivos são estudar as propriedades magnetoelásticas em alguns materiais que não são frequentemente abordados pela literatura, e avaliar a potencialidade da técnica para a análise de filmes finos. Para isto, são realizadas medidas principalmente em ligas ferromagnéticas amorfas baseadas em Co, Fe e Ni. Para a maioria das amostras analisadas, a resposta magnetoelástica é maior quando o campo magnético é aplicado na direção do eixo de fácil magnetização, de forma contrária à esperada teoricamente. São apresentadas duas investigações envolvendo filmes finos de nitreto de alumínio. Primeiro é estudado o crescimento de filmes de AlN sobre vários substratos e camadas semente. Filmes crescidos sobre vidro e poliimida apresentam excelentes propriedades estruturais para aplicações em sistemas eletromecânicos e eletrônica flexível. Amostras obtidas com baixos valores de tensão residual, sobre substratos de silício, são interessantes para incorporação em tecnologias existentes. Segundo, são investigadas bicamadas de AlN com filmes ferromagnéticos. Além das propriedades estruturais e morfológicas dos filmes de AlN, a análise das características magnéticas das estruturas contribui para o design de multicamadas que exploram o efeito magnetoelétrico. Finalmente, são abordados problemas em medidas de microscopias de varredura por sonda envolvendo campos elétricos. Imagens da superfície de filmes piezoelétricos de AlN foram coletadas sistematicamente. Entre outras observações importantes, demonstra-se que é possível adquirir imagens confiáveis de piezo-resposta em regiões fortemente polarizadas, e visualizar a formação de domínios ferroelásticos. Também é proposta uma nova técnica de microscopia, para investigar as propriedades ferro e piezoelétricas de uma amostra, explorando o efeito piezoelétrico direto. Utilizando excitação acústica e detecção elétrica, o potencial da nova técnica é demonstrado com imagens de superfícies cristalinas de quartzo e AlN.

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Dissertations / Theses on the topic 'Aluminum alloys Bauschinger effect'

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