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An Investigation Of Threshold Stress In Dispersion Strengthened Aluminum Alloys
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Book Synopsis An Investigation of Threshold Stress in Dispersion Strengthened Aluminum Alloys by : Sachin Deshmukh
Download or read book An Investigation of Threshold Stress in Dispersion Strengthened Aluminum Alloys written by Sachin Deshmukh and published by . This book was released on 2005 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The high creep resistance of dispersion-strengthened alloys is a result of a threshold stress, which is determined by the attractive dislocation-particle interaction. The change of dislocation-particle interaction with temperature and the resultant threshold stress have been identified as research areas that need focused effort to improve the fundamental understanding of creep deformation of dispersion strengthened materials. Al-6Mg-2Sc-1Zr, Al-6Mg-1Sc-1Zr-10 vol.% SiC and Al-5Y2O3-10SiC systems were chosen for this study. Conventional creep experiments were carried out at constant load to study the creep mechanism and threshold stress in creep. The temperature of creep experiment performed was in the range of 423 to 573 K. (0.4 to 0.6 T[subscript m]). Creep data obtained in all the system mentioned above ranges over 8 orders of magnitude of strain rate. The analysis of the creep data obtained in the investigation have provided information on the creep characteristics of the alloy including the shape of the creep curve, the temperature dependence of the creep rate, the stress dependence of the creep rate and the details of creep mechanism. Microstructures were evaluated using optical, scanning and transmission electron microscopy. A threshold type creep behavior was measured and explained by observed dislocation-particle interactions. When threshold stress is incorporated into the analysis, it is shown that the stress exponent is ~5 and activation energy is close to the value for lattice self diffusion of pure aluminum. These results suggest that dislocation climb in the aluminum alloy is the rate controlling the creep process in this composite. The composite showed increased creep resistance at higher temperature compared to the unreinforced alloy. The dislocation-particle interaction was studied in composite by in-situ straining experiments in a transmission electron microscope. The experiments were conducted in order to find the deformation micromechanics involved at creep temperatures. In-situ TEM straining experiment showed that dislocations spend most of the time interacting with particle during the climb by-pass processes. Particle pinning strength was determined from the dislocation curvature and critical bow-out angle before the detachment at various temperatures and compared with the experimentally observed threshold stress values. The in-situ experiments support observations of attractive dislocation particle interaction obtained in last two decades by conventional TEM. At each temperature mean detachment stress values calculated from critical dislocation configuration lower than the experimental thresholds stress indicating a contribution from load transfer to reinforcement phase. A new positive climb model is proposed for the threshold stress in dispersion strengthen alloy. The model incorporates the concept of dislocation core relaxation at the particle-matrix interface which leads to attractive dislocation-particle interaction. The model predicts a temperature dependent threshold stress and the predicated creep behavior is in reasonable agreement with the behavior of an Al-Sc alloy"--Abstract, pages iv-v.
Book Synopsis The Creep and Aging Response of a Rapidly Solidified Al-Fe-V-Si Alloy by : Robert J. Lewis
Download or read book The Creep and Aging Response of a Rapidly Solidified Al-Fe-V-Si Alloy written by Robert J. Lewis and published by . This book was released on 1990 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Survey of Dispersion Strengthening of Metals and Alloys ; [summary Technical Report by : Rointan Framroze Bunshah
Download or read book A Survey of Dispersion Strengthening of Metals and Alloys ; [summary Technical Report written by Rointan Framroze Bunshah and published by . This book was released on 1959 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Constant Amplitude and Post-overload Fatigue Crack Growth Behavior in PM Aluminum Alloy AA 8009 by :
Download or read book Constant Amplitude and Post-overload Fatigue Crack Growth Behavior in PM Aluminum Alloy AA 8009 written by and published by . This book was released on 1991 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1993 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamental Investigations of Plasticity in High Strength Nanostructured Aluminum Alloys by :
Download or read book Fundamental Investigations of Plasticity in High Strength Nanostructured Aluminum Alloys written by and published by . This book was released on 2000 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cryomilled aluminum alloys are being developed for aerospace applications. These high-strength aluminum alloys are currently targeted for low-temperature rocket applications. This research focused on the fundamental strengthening mechanisms in these alloys. The primary sources of strengthening in cryomilled aluminum alloys are dispersion of nanocrystalline particles and ultrafine grain size that form during the cryomilling stage. Optimized thermo-mechanical processing of cryomilled powder results in an ultrafine grain size material with nanocrystalline particles. This study investigated the temperature dependence of strength and ductility in these alloys. The theoretical models predict strengthening at low temperatures and decrease of flow stress with decreasing grain size because of diffusional flow and grain boundary sliding at elevated temperatures. The results from this study show discrepancies with theoretical models. Significant work hardening was observed at room temperature in both Al-Ti-Cu and Al-Mg alloys. The strain hardening exponents suggest contributions from both direct and indirect work hardening mechanisms. At elevated temperatures, the stress-strain rate data for Al-Mg alloys can be best described by a power law constitutive relationship with a stress exponent of 5 and threshold stress. However, the activation energy is very high even after compensating for threshold approach. This indicates that dissolution of Al3Mg2 precipitates influence the deformation kinetics. (6 figures, 8 refs.).
Book Synopsis Dispersed Phase Strengthening of Corrosion-resistant Aluminum by : Armour Research Foundation (U.S.)
Download or read book Dispersed Phase Strengthening of Corrosion-resistant Aluminum written by Armour Research Foundation (U.S.) and published by . This book was released on 1960 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: A program in which corrosion-resistant aluminum alloys were dispersion- strengthened by powder metallurgical methods is described. The alloy was obtained in powder form, mixed with hard, stable dispersant powders of Al2O3, AlPO4, SiO2, B4C, and SiC by various methods, compacted, and extruded. Tensile strengths of extruded rods were, in some cases, triple that of the extruded, dispersion-free powder product. Corrosion resistance of these materials was observed to be equivalent to that of the wrought dispersion-free alloy.
Book Synopsis Effects of Changing Stress Amplitude on the Rate of Fatigue-crack Propagation in Two Aluminum Alloys by : C. M. Hudson
Download or read book Effects of Changing Stress Amplitude on the Rate of Fatigue-crack Propagation in Two Aluminum Alloys written by C. M. Hudson and published by . This book was released on 1961 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of fatigue tests with specimens subjected to constant amplitude and two-step axial loads were conducted on 12-inch-wide sheet specimens of 2024-T3 and 7075-T6 aluminum alloy to study the effects of a change in stress level on fatigue-crack propagation. Comparison of the results of the tests in which the specimens were tested at first a high and then a low stress level with those of the constant-stress-amplitude tests indicated that crack propagation was generally delayed after the transition to the lower stress level. In the tests in which the specimens were tested at first a low and then a high stress level, crack propagation continued at the expected rate after the change in stress levels.
Book Synopsis High Temperature Deformation of Mechanically Alloyed Aluminum IN90211 by : Thomas Rector Bieler
Download or read book High Temperature Deformation of Mechanically Alloyed Aluminum IN90211 written by Thomas Rector Bieler and published by . This book was released on 1989 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dispersion Strengthening of Internally Oxidized Iron-aluminum Alloys by : Mark I. Copeland
Download or read book Dispersion Strengthening of Internally Oxidized Iron-aluminum Alloys written by Mark I. Copeland and published by . This book was released on 1972 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Investigation of Alloying Effects in Aluminum Dispersion Strengthened with Al$sub 2$O$sub 3$. by :
Download or read book Investigation of Alloying Effects in Aluminum Dispersion Strengthened with Al$sub 2$O$sub 3$. written by and published by . This book was released on 1975 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two types of alloying elements were investigated to determine if the room-temperature strength could be improved and if, through lowering the oxide content, the high-temperature ductility could be improved. Mg was investigated for its solid solution strengthening in one type alloy. The other type alloy involved further dispersion strengthening through adding Fe, Mo, Zr, Cr, V, and Ti which form highly stable intermetallic compounds with Al. Fabrication techniques were developed which produced uniform and reproducible rods for testing. Prealloyed powders were produced by atomizing the molten alloys and collecting the powders in water. This procedure produced uniform powders with a very fine distribution of the intermetallic compounds. Fabrication into rods then included ball-milling, vacuum hot pressing, vacuum heat treating, and hot extrusion. Mg additions improved strengths up to 200$sup 0$C with little effect above that temperature. Room-temperature tensile strengths up to 77,000 psi were obtained which are comparable to the strengths obtained in conventional aluminum alloys. The additional dispersion strengthening of the intermetallic compounds is additive to that of the oxide from room temperature to 450$sup 0$C. No significant improvements in ductility are obtained by reducing the oxide content since even at very low ball-milling times (id est, low oxide contents) the uniform elongation at 450$sup 0$C is typically 0.5 percent. Good combinations of strength and ductility at 450$sup 0$C were obtained in some of the alloys containing intermetallic compounds with no ball-milling. Typical properties at this temperature were tensile strengths of 7,000 psi, uniform elongation of 3 percent, and total elongation of 35 percent. (21 tables, 33 fig, 43 references) (auth).
Book Synopsis Fundamental Aspects of Dislocation Interactions by : G. Kostorz
Download or read book Fundamental Aspects of Dislocation Interactions written by G. Kostorz and published by Elsevier. This book was released on 2013-09-03 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III covers the papers presented at a European Research Conference on Plasticity of Materials-Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III, held on August 30-September 4, 1992 in Ascona, Switzerland. The book focuses on the processes, technologies, reactions, transformations, and approaches involved in dislocation interactions. The selection first offers information on work softening and Hall-Petch hardening in extruded mechanically alloyed alloys and dynamic origin of dislocation structures in deformed solids. Discussions focus on stress-strain behavior in relation to composition, structure, and annealing; comparison of stress-strain curves with work softening theory; sweeping and trapping mechanism; and model of dipolar wall structure formation. The text then ponders on plastic instabilities and their relation to fracture and dislocation and kink dynamics in f.c.c. metals studied by mechanical spectroscopy. The book takes a look at misfit dislocation generation mechanisms in heterostructures and evolution of dislocation structure on the interfaces associated with diffusionless phase transitions. Discussions focus on dislocation representation of a wall of elastic domains; equation of equilibrium of an elastic domain; transformation of dislocations; and theoretical and experimental background. The selection is a valuable reference for readers interested in dislocation interactions.
Book Synopsis Effect of Thermal Exposure, Forming, and Welding on High-temperature, Dispersion-strengthened Aluminum Alloy: Al-8Fe-1V-2Si by :
Download or read book Effect of Thermal Exposure, Forming, and Welding on High-temperature, Dispersion-strengthened Aluminum Alloy: Al-8Fe-1V-2Si written by and published by . This book was released on 1991 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of the Dispersion Strengthened Aluminum Or Sap Type Alloys by : John A. Dromsky
Download or read book A Study of the Dispersion Strengthened Aluminum Or Sap Type Alloys written by John A. Dromsky and published by . This book was released on 1963 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2005 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Stress-corrosion Cracking of Aluminum Alloys by : F. R. Mertens
Download or read book Stress-corrosion Cracking of Aluminum Alloys written by F. R. Mertens and published by . This book was released on 1967 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis SME Technical Paper by : Society of Manufacturing Engineers
Download or read book SME Technical Paper written by Society of Manufacturing Engineers and published by . This book was released on 2003 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
