Novel Processing for Creating 3D Architectured Porous Shape Memory Alloy
Final rept. 12 Dec 2011-11 Sep 2012
NORTHWESTERN UNIV EVANSTON IL OFFICE OF RESEARCH SPONSORED PROJECTS
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We have developed two processing methods for creating fully 3D interconnected NiTi porous structures with arrayed micro-channels. Processing with HIPing results in a fully densified matrix, though bonding at powder boundaries is limited by oxidation. The strength of the powder bonding can be increased by processing with liquid phase sintering, though the resulting matrix is not fully densified. Tailored to the specific application, both of these methods are valuable for creation of these 3D interconnected structures. The stress-strain response of these types of samples was examined through digital image correlation. The full strain field around a single and multiple pores was examined and compared to continuum modeling of the same geometry. While the transformation is captured qualitatively as it initiates below the pores and propagates 45 to the applied tensile load, continuum modeling is unable to capture the discrete with multiple pores, as the transformation bands cross and interact during deformation. Therefore while continuum modeling will clearly illustrate the trends of the deformation, as pore size and spacing approaches the granular length scale, these discrete effects cannot be captured by continuum modeling but must be examined experimentally.
- Fabrication Metallurgy