Graduate Thesis Or Dissertation
 

Exploring the Ductility Minimum of Niobium C103 at Intermediate Temperatures using Triaxial Tensile Specimens

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/v405sk387

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  • This work explores the mechanical properties of single-phase niobium alloy C103 from room temperature to 600°C for the purpose of expanding safe uses of the material into new applications. The study utilizes a symmetrically notched triaxial tensile specimens to manipulate the internal stress field in order to observe the changes in ductility, ultimate tensile strength, and fracture behavior, for the purpose of locating and characterizing the ductility minimum. Three triaxialities (0.556, 1.03, and 1.58) were tested over four temperatures (room temperature, 400, 500, and 600°C) in an argon environment. Load and displacement data were collected from the electric servomotor, and scanning electron microscopy was used for fractography and reduction of area measurements. For all three triaxialities the material reached a reduction of area local maximum, and ultimate tensile strength local minimum at 400°C, at which point both the reduction of area and ultimate tensile strength inflected and changed steadily to 600°C. The ductility minimum is beyond 600°C. Strain-aging is the likely cause of the reduced ductility at elevated temperatures, as is evidenced by the presence of Lüders Bands and Portevin-Le Châtelier effects in the stress-stroke curves. No evidence of brittle failure was found on the fracture surfaces.
  • Keywords: Alloy C103, Dynamic Strain Aging, Niobium, Ductility
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  • Thanks also to ATI, special mention for the Albany branch, for funding this project, and to Oregon Metals Initiative (OMI) for matching funds. Without your contributions this project would not have been possible.
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