An investigation of precipitation was carried out on the system Cu-Ni-Co at temperatures varying from 600°C to 800°C over a wide range of composition . The precipitation process was studied primarily by use of X-ray diffraction techniques. The precipitation was observed to procede by a spinodal decomposition process. The initial wavelength of the modulated structure was in the range 40 to 55Å, in good agreement with the theory for spinodal decomposition. On ageing, a coarsening was observed for all alloys aged inside the spinodal. This coarsening appeared to follow a law of the form Q[superscript: m] – Qo[superscript: m] = k (t-to) where Q = wavelength at time t Qo = wavelength before the coarsening begins at time to k and m = constants The activation energy of the coarsening process was found to be 65 kcal/mole + 10 kcal suggesting that volume diffusion was the controlling factor. RESUME Le présent travail étudie la formation de précipités dans divers alliages du systéme Cu-Ni-Co au cours de vieillissements à des temperatures de 600°C a 800°C. L’évolution de la précipitation a été suivie principalement par diffraction des rayons X. On a observé que la précipitation procède par décomposition spinodale. La longeur d'onde initiale de la structure modulée est comprise entre 40 et 55Å; en bon accord avec la théorie de la décomposition spinodale de Cahn. Au cours du vieillissement on a mesuré un accroissement de la longeur d'onde pourtous les alliages traités à l'intérieur du spinodal. Cet accroissement de longeur d'onde obéit à une loi de la forme Q[superscript: m] – Qo[superscript: m] = k (t-to) ou Q = longeur d'onde au temps t Qo = longeur d’onde avant que le grossisement commence, à to k et m = constantes if energie d'activation du mécanisme de croissance des précipités a été déterminée; sa valeur, 65 kcal/mole suggére que la diffusion en volume est le facteur préponderant. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

No description available.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 193-199).

Made available in DSpace on 2014-10-09T12:29:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:17Z (GMT). No. of bitstreams: 1 01057.pdf: 4184431 bytes, checksum: 2caaae91c80ebe87973209e0f0f2ba56 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Energia Atomica - IEA

Made available in DSpace on 2014-10-09T12:29:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:17Z (GMT). No. of bitstreams: 1 01057.pdf: 4184431 bytes, checksum: 2caaae91c80ebe87973209e0f0f2ba56 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Energia Atomica - IEA

Mode I and Mode III fatigue tests were performed on copper nickel alloys in helium, salt water environments. The hydrogen, oxygen, two alloys used air and in this investigation were 90-10 and 70-30 copper nickel. Both alloys contained iron which was added to improve the erosion corrosion resistance. The extent of cracking varied with the test environment. Tests showed that oxygen and humid air promoted cracking while salt water helium was used as the baseline retarded cracking when environment. Hydrogen promoted cracking when compared to helium but retarded cracking if comparisons were made with oxygen or humid air. The environmental effects (helium as the base case} in the Mode I tests in gaseous environments were manifested in the form of shorter fatigue lives, easier crack initiation, marginally higher crack growth rates and the development of intergranular fracture at the surface. These effects were accompanied by a change in the near surface deformation characteristics. The increases in fatigue life induced by testing in aqueous environments were greatly extended if the copper nickel was galvanically coupled to steel. Mode III tests showed the same ranking of environmental effects as Mode I tests and also showed multiple initiation, brittle fracture and secondary cracking. Two models were proposed to explain the observed results. One was based on the dilation-aided diffusion of oxygen ahead of the crack tip and subsequent oxidation of internal iron particles. The oxidation caused a volume expansion which produced internal tensile strains and facilitated fracture. The other mechanism was based on dilation-aided transport of hydrogen with subsequent accumulation of hydrogen at interfaces, resulting in a lowering of the interfacial strength and promoting intergranular fracture. The observed increases in life in the aqueous environments were rationalized by the reduced oxygen content available in the stagnant solutions. These observations suggest that the presence of iron accelarates fatigue in copper nickel alloys exposed to aggressive environments. Thus, any application involving fatigue loading with simultaneous exposure to aggressive environments should attempt to ensure that the iron content of the copper nickel alloys is minimized. / Doctor of Philosophy

Call number: LD2668 .T4 1962 A82

This investigation was initiated by IBM to determine the types of cracks formed in hot-isostatic-pressed (HIP) Ni-Zn ferrite under impact and static loading conditions. A 1/8-inch tungsten carbide (WC) ball was used to apply the load in both cases. The impact loading condition was accomplished by dropping the WC ball from various heights between 40 and 200 cm. The static loading condition was accomplished by applying loads of 10 kg, 15 kg, and 30 kg on a Rockwell Hardness Tester. The response of HIP Ni-Zn ferrite to impact and static loading was elastic/plastic yielding permanent indentations. "Dimple" impressions, Hertzian-ring cracks, and radial cracks were formed upon applying increasing loads to the HIP Ni-Zn ferrite. As the grain size of the material was increased, both the Hertzian-ring and radial cracks were formed at lower loads compared to the as-received samples. The "dimple" impressions were not observed to follow this trend.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Includes bibliographical references. / by Charles Hubert Smith. / Ph.D.

"April 1999." Includes bibliographical references (leaves 46-51). Aims to collect information about the numbers of dental workers who are sensitive or allergic to nickel and to help identify signs which might predict those people who are most likely to be sensitive to nickel. Uses a standard patch test to identify sensitive subjects.