The basic assumption of limit design, that moments are equalized by the formation of a mechanism has proven applicable to steel beams and certain types of frames. It is not known, however, if the theory applies to light metal alloys. Steel possesses a considerable amount of strain hardening which is essential to the formation of plastic hinges in the beam, but some aluminum alloys which have little strain hardening may not be suitable for limit design. Two beam tests were carried out on a twice statically indeterminate beam made of Alcan 65S-T6 aluminum alloy to determine whether the mechanism predicted by the theory of limit design is realized before failure occurs in the beam. Moments and deflections of the beam near failure are compared with theoretical predictions obtained from the theory of limit design and the theory of inelastic bending. The latter, developed by Dr. A. Hrennikoff in 1918, is more "exact" than the theory of limit design. Test results showed that the beam failed at one of the early plastic hinges, before the mechanism was fully developed. It demonstrated that limit design is not always applicable to beams made of aluminum alloys which have very little strain hardening. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Although investigations have shown that the theory of limit design applies to beams and some frames made of mild steel, it is not certain whether it applies in the same way to the light alloys. Steel frames satisfy the limit design prediction of a failure mechanism not only because steel is very ductile but also because steel exhibits strain hardening. Light alloys such as high-strength aluminum alloy exhibit very little strain hardening. Two load tests were carried out on redundant beams made of the aluminum alloy to see if the mechanism condition of limit design was reached before failure took place in the beam. Measurements of beam deflections and moments are compared to the deflections and moments predicted by the theory of inelastic bending. The theory of inelastic bending is based on the stress-strain diagram and takes account of strain hardening and a failure strain. Tables of unit functions derived from the stress-strain diagram of the aluminum alloy are presented for use with the inelastic bending theory. In both tests, the mechanism condition of limit design was reached before failure took place. Shortly after the mechanism condition was reached, a fracture occurred in the flange on the tension side of the beam. Thus the type of failure indicates that not all structural configurations will achieve the mechanism condition. Beyond the limit of elastic deformation (17 kips load) and up to a load of about 27 kips, the beam moments were similar to those predicted by the inelastic bending theory. From 27 kips load to failure at 32 kips, the moments were distributed in the beam differently than the predicted moments due to the presence of high shear force. The load-deflection curves are the same as the curves from the theory, although measured deflections were always greater. The ultimate curvature at the section of failure was greater than predicted from the theory. There were some shortcomings of the tests. The tests were originally set up to be unfavourable towards the limit design theory. However, stiffeners were added at the plastic hinge locations to prevent web failure, and the presence of the stiffeners was helpful in allowing redistribution of moments to take place in much the same way as strain hardening does in steel beams. Also the presence of the stiffeners and stiffener holes made interpretation with the inelastic bending theory uncertain. Finally there were some errors in measuring the moments by means of strain gauges. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Activities of sodium in alumina-saturated cryolite-aluminum melts have been measured by the equilibration of a three phase system of cryolite, aluminum and lead. An approximate linear increase in the activity of sodium was noted on a log plot of activity as a function of NaF-A1F₃ weight ratios over the range pertinent to commercial reduction cell operation. Activities of sodium in cryolite-aluminum melts have been calculated by employing the equilibrium reaction between cryolite and aluminum metal and the thermodynamic data from-an analysis of the NaF-A1F₃ phase diagram. Differences between the reversible deposition potential for aluminum and sodium at one atmosphere partial pressure were calculated from the measured equilibrium sodium activities. The values obtained were of the order of .15 to .4O volts, increasing with decreasing NaF-A1F₃, ratio. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The theory of limit design originally was developed for structural steel construction. Tests carried out on mild steel beams and frames are in agreement with the theory. Unfortunately a limited number of tests have been carried out on other ductile materials such as light alloys. Therefore more tests are required in order to investigate whether the theory of limit design is also applicable, with or without modification to aluminum alloys. The failure mechanism predicted in limit design materializes in steel frames not only because steel is very ductile but also because steel has strain hardening. Aluminum alloys exhibit very little strain hardening. In the research described here there were two objects. The first object was to investigate the applicability of limit design to aluminum alloys. The second object was to check experimentally the theory of inelastic bending. Three load tests were carried on continuous beams made of aluminum alloy to see if the mechanism condition was attained before failure of the beam. Moments and deflections predicted by the theory of inelastic bending were compared against measurement of beam moments and deflections. The theory of inelastic bending considers the effect of strain hardening. Tables of unit function derived from the stress-strain diagram of aluminum alloy (65S-T6) are presented so that they may he used when the theory of inelastic bending is applied. The first test failed prematurely due to crippling of the compression flanges. In the second and the third test the mechanism condition of limit design was reached shortly before failure of the tension side of the beam under the load point by fracture. Thus the type of failure indicates that not all structures will achieve the mechanism condition. The failure load and the ratio of moments at failure, as predicted by the theory of inelastic bending was equal to 15.53 Kips and 1.13 respectively. Test results indicated a failure load of 16 Kips and a ratio of moments at failure equal to 1.1. The load-deflection curves were the same as the curves from the theory. At failure the deflection under the load was 5.57 inches compared to computed theoretical deflection of 5.46 inches. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Sodium activity data has been obtained for the sodium - aluminum system for sodium concentrations in aluminum between N[subscript Na] = 25 x 10-⁶ and 75 x 10-⁶. Additional data has allowed the calculation of activity data up to N[subscript Na] = 300 x 10-⁶. The concentration interval N[subscript Na] = 25 x 10-⁶ to 300 x 10-⁶ encompasses those sodium concentrations normally found in commercial pot-line operation. The sodium activity data has been collected by using a two-phase distribution equilibration of sodium between a lead-rich and an aluminum-rich phase. The sodium-lead system was used as a reference for the determination of the activity of sodium. The sodium exhibits large positive deviations from ideality in the sodium-aluminum system. The sodium activity shows a strong dependence on the sodium concentration of the aluminum phase for sodium concentrations below N[subscript Na] = 100 x 10-⁶. The activity data for aluminum in the sodium-aluminum system has been obtained by the Gibbs - Duhem integration of the sodium activity data. The data for the aluminum indicates that the activity of aluminum can be considered equal to its mole fraction over the entire range of miscibility of the sodium-aluminum system. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The objective of this study is to evaluate material response to plastic deformation between aluminum alloys AA2219-T87 and AA2195-T87. Of particular interest are the deformation conditions that result in subsequent grain refinement or recrystallization. Although both alloys have a face centered cubic (FCC) microstructure, variations are expected in their plastic deformation behavior. During plastic deformation, dislocation motion results in faulted regions whose width can vary according to chemical composition of the alloy. These faulted regions, or stacking faults, influence whether dislocation entanglements form or annihilation occurs during the deformation process. In addition, differences in mechanical properties can affect the amount of adiabatic heating that occurs during deformation. Ultimately these differences can affect the uniformity of deformation and the stability of the microstructure.

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Chung, Kam Chuen = 鐵基/鐵三鋁基/鋁基金屬基複合材料的合成和表徵 / 鍾錦銓. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Chung, Kam Chuen = Tie ji/tie san lü ji/lü ji jin shu ji fu he cai liao de he cheng he biao zheng / Zhong Jinquan. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.v / Table of contents --- p.vi / List of tables --- p.x / List of figures --- p.xi / Chapter Chapter 1 --- Introduction --- p.1-1 / Chapter 1.1. --- Metal matrix composites (MMCs) --- p.1-1 / Chapter 1.1.1. --- Introduction --- p.1-1 / Chapter 1.1.2. --- Matrix materials --- p.1-1 / Chapter 1.1.3. --- Reinforcements --- p.1-2 / Chapter 1.1.4. --- Fabrication techniques --- p.1-3 / Chapter 1.1.5. --- Applications --- p.1-7 / Chapter 1.2. --- MMCs in this work --- p.1-9 / Chapter 1.2.1. --- Metal matrices --- p.1-9 / Chapter 1.2.2. --- Reinforcements --- p.1-11 / Chapter 1.3. --- Previous works --- p.1-13 / Chapter 1.4. --- Objectives and current works --- p.1-15 / Chapter 1.5. --- Thesis layout --- p.1-16 / References --- p.1-18 / Chapter Chapter 2 --- Methodology and Instrumentation --- p.2-1 / Chapter 2.1. --- Powder metallurgy (PM) --- p.2-1 / Chapter 2.1.1. --- Mixing --- p.2-1 / Chapter 2.1.2. --- Compacting --- p.2-1 / Chapter 2.1.3. --- Sintering --- p.2-2 / Chapter 2.2. --- Sample preparation --- p.2-3 / Chapter 2.2.1. --- Mixing and compacting --- p.2-3 / Chapter 2.2.2. --- Tube furnace sintering --- p.2-3 / Chapter 2.2.3. --- Arc melting --- p.2-4 / Chapter 2.3. --- Sample characterization --- p.2-4 / Chapter 2.3.1. --- DTA and DSC --- p.2-5 / Chapter 2.3.2. --- XRD --- p.2-6 / Chapter 2.3.3. --- SEM --- p.2-6 / Chapter 2.3.4. --- TEM --- p.2-6 / Chapter 2.3.5. --- Microhardness test --- p.2-7 / Chapter 2.3.6. --- VSM --- p.2-7 / References --- p.2-9 / Chapter Chapter 3 --- Synthesis of magnetic hercynite in Fe-based MMC --- p.3-1 / Chapter 3.1. --- Introduction --- p.3-1 / Chapter 3.2. --- Experiments --- p.3-2 / Chapter 3.3. --- Results and discussion --- p.3-2 / Chapter 3.3.1. --- DTA and XRD results --- p.3-2 / Chapter 3.2.2. --- SEM and EDS results --- p.3-3 / Chapter 3.3.3. --- Reaction mechanisms --- p.3-5 / Chapter 3.3.4. --- Thermodynamic model for the reactions --- p.3-8 / Chapter 3.3.5. --- Saturation magnetization --- p.3-9 / Chapter 3.3.6. --- Microhardness --- p.3-11 / Chapter 3.4. --- Conclusions --- p.3-11 / References --- p.3-13 / Chapter Chapter 4 --- Synthesis of reinforced Fe3Al-based MMC --- p.4-1 / Chapter 4.1. --- Introduction --- p.4-1 / Chapter 4.2. --- Experiments --- p.4-2 / Chapter 4.3. --- Results and discussion --- p.4-4 / Chapter 4.3.1. --- AI2O3-reinforced samples --- p.4-4 / Chapter 4.3.2. --- MgO-reinforced samples --- p.4-8 / Chapter 4.3.3. --- MgAl204-reinforced samples --- p.4-11 / Chapter 4.3.4. --- Microhardness and densities --- p.4-14 / Chapter 4.4. --- Conclusions --- p.4-16 / References --- p.4-18 / Chapter Chapter 5 --- Formation of Al-Fe intermetallics in Al-based MMC…… --- p.5-1 / Chapter 5.1. --- Introduction --- p.5-1 / Chapter 5.2. --- Experiments --- p.5-2 / Chapter 5.3. --- Results and discussion --- p.5-3 / Chapter 5.3.1. --- DTA and XRD results --- p.5-3 / Chapter 5.2.2. --- "SEM, TEM and EDS results" --- p.5-4 / Chapter 5.3.3. --- Reaction mechanisms --- p.5-9 / Chapter 5.3.4. --- Phase transformation in solidification --- p.5-11 / Chapter 5.3.5. --- Microhardness --- p.5-13 / Chapter 5.4. --- Conclusions --- p.5-14 / References --- p.5-15 / Chapter Chapter 6 --- Conclusions and future work --- p.6-1 / Chapter 6.1. --- Conclusions --- p.6-1 / Chapter 6.2. --- Future work --- p.6-3

This study determined the independent effects of various homogenization cycles and precipitation treatments on the elevated temperature workability and the final ambient temperature mechanical properties of AA2024 aluminum alloy and on the T3 tensile properties of 2014 aluminum alloy as well as T6 tensile properties of 2618 and 2618 (Curich) aluminum alloys. The elevated-temperature tensile and extrusion tests indicate that the workability of AA2024 alloy improves with elevated-temperature precipitation treatment as suggested by earlier investigations. The precipitation treatments do not appear to degrade the ambient-temperature T3 and T8 tensile properties. The time at the precipitation temperature appears to affect the T3 and T8 tensile properties in unextruded ingot, longer times especially providing both relatively high ambient-temperature strength and ductility of AA2024 alloy. The time at the standard homogenization temperature and the heat-up and cool-down rates do not dramatically affect the T3 tensile properties of unextruded ingot of AA2024 and 2014 alloys. However, long soak times at the homogenization temperature and more rapid cooling rates may improve the properties somewhat of AA2024 alloy and longer heat-up times and rapid cooling rates may slightly improve the properties of 2014 alloy. The higher standard solution temperature appears to increase both strength and ductility of 2014 alloy over lower temperatures. The homogenization temperature affects the T6 tensile properties of 2618 and 2618 (Cu-rich) alloys, a high homogenization temperature (compare to standard homogenization temperature) providing both high strength and ductility. Increased manganese and copper appears to increase the strength, but slightly decreases the ductility. The standard aging temperature and time produce higher strength but lower the ductility than lower temperatures at the same or shorter aging times in 2618 (Cu-rich) alloy. / Graduation date: 1993

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 86-89). Also available on the Internet.