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Poster

Characterisation of NiTi cellular materials fabricated by the powder-metallurgy spaceholder technique

Wednesday (24.10.2018)
19:48 - 19:51
Part of:
Line-Up:
- Poster Battery housings for electric vehicles using CFRP and aluminium foam 0 Joachim Baumeister
- Poster Manufacturing and characterization of open-cell stainless steel foams by investment casting 1 Jan Frömert
- Poster Interface formation of Mg2X (X = Si, Sn) in cellular Si infiltrated by Mg(Sn) alloys 1 Alexander M. Matz
- Poster Production of microcellular PMMA using the bead foaming technology 1 Mikel Mugica
- Poster Nanocellular PMMA with tunable cellular structure by changing the rheological behaviour of the polymer matrix. 1 Judith Martín de León
- Poster Production of thermoplastic polyurethane foams synthesized with different contents of hard segment and graphene nanoplatelets by the gas dissolution foaming process 1 Ph.D. Mercedes Santiago-Calvo
- Poster Surface functionalized filters for aluminum melt filtration 1 Dr.-Ing. Claudia Voigt
- Poster Nanocellular polymers based on PMMA/sepiolite nanocomposites: characterization of the mechanical behaviour 1 Victoria Bernardo
- Poster Impact resistant foams based on PP/POE blends 1 Ph.D. Santiago Munoz Pascual
- Poster Crosslinked open cell ethylene butyl acrylate copolymer (EBA) foams: properties and applications 1 Ph.D. Eduardo López
- Poster Influence of molecular weight in the solubility,diffusivity and the subsequent cellular structure of polystyrene foams 1 Ph.D. Alberto Ballesteros
- Poster Crushing strength measurement at reticulated ceramic foams ex situ and in situ CT analysis 1 Dr.-Ing. Claudia Voigt
- Poster Initiation of plateau region during compression test of porous metals with aligned unidirectional pores 1 Tomoya Tamai
- Poster Active meta-materials with adjustable pore size 1 Dr. Reza Hedayati
- Poster Polymeric foams 3D numerical mechanical modelling 1 Stefano Tagliabue
- Poster Characterisation of NiTi cellular materials fabricated by the powder-metallurgy spaceholder technique 1 Dr. Karl Dahm
- Poster Accurate separation of open cell metal foams using remote laser cutting technique 1 Robert Baumann
- Poster Generation of artificial foam structures and evaluation of their thermo-mechanical, flow and filtration characteristics (Poster) 1 Christoph Settgast
- Poster Surface modification of magnesium-based foams by Directed Plasma Nanosynthesis 1 Viviana Marcela Posada Pérez

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Nickel titanium (NiTi) shape memory alloys are promising biomaterials for bone replacement applications, as they show similar bio-mechanical properties to human bone as well as high biocompatibility and good corrosion resistance. NiTi alloys also exhibit properties such as super-elasticity or shape memory effects - offering opportunities in tailored mechanical properties that are not available with other metallic biomaterials. This investigation was aimed at creating cellular NiTi materials with elastic moduli close to that observed for cortical bone. The cellular samples were fabricated using pre-alloyed spherical NiTi powder, a polymer binder and urea as the spaceholder. The urea particles were spherical with a narrow size distribution between 1.68 and 2.00 mm. Vacuum sintering conditions were optimised initially using non-spaceholder samples (NiTi powder + polymer binder only) to reduce micro-porosity below 5%. This required long sintering times close to the observed melting point of the NiTi. Microindentation studies confirmed that the dense material exhibited large elastic recovery in the as-sintered state. These sintering conditions were then used to produce cellular samples with interconnected macro porosity levels at 50 and 55 vol%. Incremental compressive loading-unloading tests demonstrated that all of the macro-porous samples displayed super-elasticity in the as-sintered condition. The 50 vol% macro-porous samples showed consistent super-elastic behaviour recovering 85-90% of stain when compressed to a maximum strain of 4%. The 55 vol% macro-porous samples on the other hand showed much more variable behaviour. The measured elastic modulus of all samples lay between 17 and 7 GPa, higher for the 50 vol% macro-porous samples than the 55 vol% macro-porous samples. The elastic modulus for all samples decreased with increasing residual strain. While samples were successfully made for mechanical testing, the fragility of the materials after thermal debinding was a major challenge.

Speaker:
Dr. Karl Dahm
Callaghan Innovation Ltd.
Additional Authors:
  • Katharina Gabrysiak
    Technische Universität Dresden
  • Dr. Pauline Calloch
    Callaghan Innovation Ltd.