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The effect of small additions of titanium on the incubation period of isothermally transformed zirconium-niobium alloy.

University of British Columbia

The general effect of small additions of titanium on the incubation period preceding the β → α + β reaction in an isothermally transformed zirconium - 17.6% niobium alloy has been studied by observing electrical resistance at constant temperature, by making micro-hardness tests, by examining specimens metallographically and by employing X-ray diffraction methods. It was found that the effect of increasing the amount of titanium was to lengthen the incubation period. According to the electrical resistance data, an alloy containing 5% titanium shows an incubation period of approximately 15 minutes while one containing 15% titanium shows a period of approximately 25 minutes at 600°C. Micro-hardness tests show the same general effect; however, corresponding incubation periods for the same alloys are approximately 30 minutes and 40 minutes. Although metallographic and X-ray diffraction results did not conflict with these conclusions, it has been pointed out that more data and some refinement in technique are needed in order that these might be employed to support resistance data with confidence. The presence of a hydride phase in quenched and partially transformed specimens was noted. The effect of this phase on the mode and rate of reaction is unknown. Clearly, further investigation is necessary if its effect on the transformation must be determined. It has, however, been shown that the method of observing transformations in this system with electrical resistance is both effective and sound.

Text

2011-12-14

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http://hdl.handle.net/2429/39695

Metals and Materials Engineering

University of British Columbia

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