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An experimental investigation into the growth and closure behaviour of small corner cracks has been conducted on a low carbon steel (ASTM A516 Grade 70). This ferritic/pearlitic steel has been chosen to investigate the complexities of small crack behaviour in the dual phase material. Innovative procedures are used for compliance measurement and opening load determination. The closure and growth behaviour of the small comer cracks are presented in terms of shape and size. The results are divided into two stages, the first pertaining to the "stationary crack", and the second dealing with the crack as it grows. The cracks are shown to exhibit an irregular growth rate, which is in part, shown to correspond with microstructural features of the material. In the short crack regime, the linear fracture mechanics parameter, AK does not correlate with the data and the use of a AKen based on the effective applied load provided little improvement.

This report provides a brief overview of the activities and accomplishments of the Metals and Ceramics (M&C) Division during the period October 1991 through December 1992. The division is organized to provide technical support, primarily in the area of high-temperature materials, for the various technologies being developed by the U.S. Department of Energy (DOE). Activities span the range from basic research (through applied research and engineering development) to industrial interactions (through cooperative research and a strong technology transfer program). The division is organized in functional groups that encompass nearly ali of the disciplines needed to develop and to apply materials in high-temperature applications. Sections 1 through 5 describe the different functional groups; Sect. 6 provides an alternative view of the division in terms of the major programs, most of which cross group lines; and Sect. 7 summarizes external interactions including cooperative research and development programs, educational activities, and technology transfer functions. Appendices describe the organizational structure, note personnel changes, present honors and awards received by division members, and contain listings of publications completed and presentations made at technical meetings. instantaneousinformationregardingboth uniformand localizedcorrosionprocessesand does not require the use of a reference electrode. EN will initiallybe applied in the model boiler tests to be performed for the NPR-MHTGR in cooperation with ABB-Combustion Engineering inChattanooga, Tennessee.Tasks on the high-temperaturecorrosion of advanced aluminides and intermetallics were conductedfor the Fossil Energy Program as part of overall alloy development initiatives. Recent ORNL results had shown significant improvement in the roomtemperatureductilityof iron aluminideswhen aluminumconcentrationsare reduced to the 16 at. % level. Therefore,we initiateda studyto define the criticalconcentrationof this element for resistance in high-temperature oxidizing and oxidizing/sulfidizing environments.These have been determinedto be 18 and 20 at. % AI for H2S-H20-H2 and air environments,respectively. Adding 5% chromiumto the 16 at. % AI alloys significantlyimproved the equi,.alent of Fe3AI (28 at. % AI) in terms of air-oxidation resistance. We also initiated a cyclic oxidation experiment with iron aluminides containing16 to 28 at. % Ai and found beneficialeffect of small additionsof zirconium on ',._cal9 adherencefor Fe3AI alloys. Iron aluminideswith 16 at. % AI and additionsof chromium (5%) and zirconium (0,1%) were superior in scaling resistance to binary alloys of 16 and 20 at. % AI and exhibited weight changes comparable to the Zr-containing Fe3AI alloys.A relatedtask in suppo,'t of the FossilEnergyProgramentailedthe developmentof phase stability diagrams for silicon carbide in the presence of sodium contaminants as contained in typical coal gasifier and pressurized fluidized-bed combustion environments.These resultshaveprovidedguidanceto the developmen...

The story of the Metals and Ceramics Division is the story of its people and the work they did, as well as the projects that resided in the Division or that the Division contributed to. Many people wrote and rewrote reams of paper trying to pull this document together, and those who wrote various sections (whether used or not) are listed below.Those who are not listed are the rest of you;you rummaged around in your memories to provide facts and anecdotes, typed documents for others, proofread drafts, and so on. And mainly, you did the outstanding work that gave this Division a story to tell. Thanks to all of you for 50 interesting and productive years. That the various forms of radiation emanating from radioactive isotopes or from the nuclei of fissioning uranium would produce damage or change the form of the materials through which the radiation passed was known much before the Manhattan Project and the genesis of Oak Ridge.Immediately after the war, some of the scientific staff of the project began publishing in the scientific literature speculations, mainly based on theoretical considerations, about the potential deleterious effects on the materials that might be used in constructing nuclear power plants.oak ridge involved in studying radiation effectsThe recognition of these possible effects on materials led to experimental and theoretical programs at the Atomic Energy Commission laboratories throughout the country, including ORNL. Initially, the Chemistry Division began to study the effects of gamma rays and neutrons on ceramics, and the Physics of Solids group (then part of the Metallurgy Division) began theoretical and experimental work on the effects of neutrons on metals.During the early 195Os, it was recognized that these property changes would have significant effects on the design of nuclear power plants. The Metals and Ceramics Division then began to determine the influence of these effect.Commercial alloys hardened and decreased in ductility in a way qualitatively similar to the earlier observations in pure metals. This "damage," however, tended to disappear as the temperature of the alloy was raised into the range useful in power plants.A In 1953, the Division was involve,d with the project to develop a nuclear reactor for aircraft propulsion; such a reactor required high-temperature performance. A high-temperature structural alloy, Inconel600, was used for the reactor. After irradiation, the stress rupture resulted from helium produced by transmutation reactions involving boron-10 in the alloy; simply put, the gas accumulated at the grain boundaries in the alloy and weakened them. Nanstad's group the emphasis is on the embrittlement and radiation-induced elevation in the ductile-to-brittle transition temperature in ferritic steel pressure vessel alloys. In Tim Burchell's group the emphasis is on radiation effects in carbon and carbon composite materials, including changes in mechanical and thermophysical properties. In Lou Mansur's group, the emphasis is on understanding the mechanisms of radiati...

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