Download or read book Microstructure Studies of Polycrystalline Refractory Oxides written by J. B. Mitchell and published by . This book was released on 1962 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: The elastic modulus and transverse bend strength of pure, dense alumina and magnesia specimens were determined as a function of grain size (1 to 250 microns) and temperature over the range of 30 to 1500 C. The elastic modulus of both com pounds was found to be essentially independent of grain size over the temperature range covered. The transverse bend strength of fine-grain-size alumina was found to be substantially greater than larger-grain-size alumina over the entire temperature range although, at the highest temperatures, the rate of decrease of strength with temperature was greatest for the fine-grain material. The transverse bend strength of magnesia was less dependent on grain size than the alumina; and, in addition, this dependence showed further decreases with temperature. At higher temperatures, the larger-grain-size speci mens exhibited greater strengths than the fine grain magnesia. (Author).
Download or read book Microstructure Studies of Refractory Polycrystalline Oxides written by William H. Rhodes and published by . This book was released on 1969 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several facets of the effect of microstructure and chemistry on the mechanical properties of magnesia and alumina were studied. Comparison of the deformation properties of high purity Al2O3 with a standard research grade of Al2O3 + 1/4% MgO demonstrated high purity material possessed a normalized creep rate approximately a factor of five (5) lower and a higher strain rate sensitivity suggesting an increased importance of diffusional creep. At strains from 3-12% evidence was obtained for strain hardening, a Bauschinger effect and polygonization which suggested considerable dislocation and grain boundary sliding activity. Also, high temperature stress-strain curves showed evidence for blunting a potentially catastrophic failure event. Al2O3 press forging experiments resulted in a better understanding of deformation and primary recrystallization processes. Bend tests of a uniform 8 micron grain size textured body demonstrated higher elevated temperature strength than 1-2 micron hot pressed Al2O3 suggesting a real benefit from the textured structure resulting from one of a number of potential models. Dead load stress corrosion studies on polycrystalline MgO demonstrated that the shape of the stress corrosion curve was dependent on the starting chemistry and/or minor grain boundary phases. Also, the resistance to dead load was markedly influenced by the introduction of 1 molar dimethyl formamide which had been shown to affect dislocation mobility in MgO.
Download or read book Technical Abstract Bulletin written by and published by . This book was released on with total page 908 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Government Research Reports written by and published by . This book was released on 1963 with total page 814 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Microstructure Studies of Polycrystalline Oxides written by William H. Rhodes and published by . This book was released on 1969 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dead load-time to failure studies on polycrystalline MgO exhibited a decreasing load bearing capacity with time which was interpreted by the Charles and Hillig stress corrosion model. The possibility of a mechanical model similar to that invoked for metals was considered and not ruled out. Chemical polishing of polycrystalline Al2O3 was accomplished, but mechanical tests failed to show a statistically valid strength improvement. Only a thermally etched surface from an earlier study exhibited a pronounced surface sensitivity to fracture strength, and dry testing conditions were required to unequivocally demonstrate this effect. Two new grades of high purity Al2O3 and MgO powders were fabricated, and mechanical testing of the Al2O3 showed equivalent brittle strengths and increased creep resistance when compared with less pure material with an equivalent microstructure. The explanation for the creep resistance may be either a slight increase in grain size which accompanied the test or decreased diffusivity due to the increased purity. Preliminary grain growth studies on high purity MgO indicate a normal grain growth behavior, but about an order of magnitude slower rate than 99.4% MgO. Press forging of polycrystalline Al2O3 was directed toward solving the engineering and process control problems of forging material with a high in-line optical transmission.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1973 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government wide Index to Federal Research Development Reports written by and published by . This book was released on 1966-05 with total page 778 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanical Properties of Ceramics and Composites written by Roy W. Rice and published by CRC Press. This book was released on 2000-04-18 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review, evaluation, and summary of the dependence of mechanical properties on grain and particle parameters of monolithic ceramics and ceramic composites. Emphasizing the critical link between fabrication and ceramic performance, the book covers the grain dependence of monolithic properties and the dependence of ceramic, composite properties on grain and particulate parameters. It includes theoretical and conceptual background, pertinent models, experimental results, a data review, discussion, and a summary or recommendations. Illustrations feature microstructural details while graphs plot data on material hardness, compressive strength, and other pivotal variables.
Download or read book NBS Special Publication written by and published by . This book was released on 1979 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Government Research Reports written by and published by . This book was released on 1963 with total page 1322 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Microstructure Studies of Polycrystalline Refactory Oxides written by A. H. Heuer and published by . This book was released on 1967 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hot working polycrystalline alumina, utilizing a press forging technique, was extensively investigated. Primary recrystallization followed the working and resulted in either single crystals (strain-anneal technique) or relatively fine-grained structures. The basal texture present after recrystallization was identical to the deformation texture; this and the equiaxed recrystallized structures suggested that oriented nucleation was important. At larger grain sizes, an elongated grain structure was observed and was attributed to oriented growth. The marked basal texture suggested that basal slip was the predominant deformation mode; the probability of other deformation mechanisms was also discussed. Addition of 1/4% MgO retarded recrystallization and a number of such samples, possessing a pronounced basal deformation texture, were used for mechanical properties determination. The working led to no less of structural integrity, and the strength was surprisingly constant with grain size, at least in the range 3.5-10.5 microns. The larger-grained worked samples were stronger than hot-pressed samples of equivalent porosity and grain size. The high ductility, up to 75% height reduction being achieved without much difficulty, suggested that hot working could be used to produce shaped bodies.
Download or read book Mechanical and Thermal Properties of Ceramics written by J. B. Wachtman and published by . This book was released on 1969 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Properties and Microstructure written by R. K. MacCrone and published by Elsevier. This book was released on 2013-10-22 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Materials Science and Technology, Volume 11: Properties And Microstructure covers the parameters important to understanding microstructural effects. The book discusses the direct observation and characterization of defects in materials; the cause and effect of crystal defects in silicon integrated circuits; as well as the microstructure of some noncrystalline ceramics. The text also describes microstructural defects in the important semiconductors silicon and germanium, microstructural effects in glasses, microstructural effects on the mechanical properties of ceramics, and finally, microstructures in ferrites. Materials scientists, materials engineers, and graduate students taking related courses will find the book invaluable.
Download or read book U S Government Research Development Reports written by and published by . This book was released on 1970 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultrafine Grain Ceramics written by John Burke and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Army Materials and Mechanics Research Center has conducted the Saga more Army Materials Research Conferences, in cooperation with the Metallurgi cal Research Laboratories of the Department of Chemical Engineering and Metallurgy of Syracuse University, since 1954. The purpose of the conferences has been to gather together scientists and engineers from academic institutions, industry, and government who are uniquely qualified to explore in depth a sub ject of importance to the Army, the Department of Defense and the scientific community. Grain size and its control is a major factor governing the behavior of materi als. Knowledge that one can obtain grain sizes in the 10 micron down to sub micron range has established the basis for a new technology. This volume, Ultrafine-Grain Ceramics, addresses itself to the broad areas of: realization of fine-grain ceramics; preparation of ultrafine particle size materials; characterization of ultrafine particles and ultrafine-grain ceramics; processing and behavior of ultra fine-grain ceramics. The technical advice provided by Dr. S. K. Dutta of the Army Materials and Mechanics Research Center during the editing of this book is acknowledged. The continued active interest and support of these conferences by Dr. E. Scala, Director, Lt. Col. Joseph B. Mason, Commanding Officer, and J. F. Sullivan, Deputy Technical Director, of the Army Materials and Mechanics Re search Center is appreciated.
Download or read book Sagamore Army Materials Research Conference Proceedings written by and published by . This book was released on 1966 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Summary of the Tenth Refractory Composites Working Group Meeting written by L. N. Hjelm and published by . This book was released on 1965 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt:
