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Monday, May 8, 2006 - 12:10 PM
MEM1.5

The Significance of Melt Practice on Fatigue Properties of Superelastic NiTi Fine Diameter Wire

M. M. Patel, D. L. Plumley, R. Bouthot, Fort Wayne Metals Research Products Corporation, Fort Wayne, IN; J. L. Proft, Metallurgical Solutions, Redwood City, CA

In continuation of a previous comparison of the influence of melt practice and strain amplitude on Ni 56wt%-Ti 0.267 mm wire, this investigation explores the fatigue properties at 0.127 mm of the same melt lots.  By employing the same rotary beam fatigue testing, material with equivalent thermo-mechanical processing to achieve like superelastic properties is compared.  With known statistically detectable variations in carbon level and inclusion content, testing again focused on determining if there is a difference in rotary beam fatigue performance.  In contrast to the results of the previous study, there is evidence of a difference in performance for the smaller diameter wire among melt sources.  Possible explanations for this difference and its significance are discussed.

Summary: This work is a continuation study which compares the influence of melt practice and strain amplitude on Nitinol wire at 0.267mm and at 0.127 mm. Rotary beam fatigue testing, was used on material with equivalent thermo-mechanical processing.