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Production of Porous Ti and Ti-26Nb-1Si Via Powder Metallurgy Method andInvestigation Some of Their Physical and Mechanical Properties

Zamani, Mohammad Hasan | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40175 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Abachi, Parvin; Ziaei Moayyed, Ali Akbar
  7. Abstract:
  8. Porous titanium and titanium alloys products are proper to use as implants which because of good properties such as high corrosion resistance, good biocompatibility, high strength to weight ratio and low elastic modulus. Porosity induces a decrease in elastic modulus and an increase of bioactivity. In present work, porous specimens of pure titanium and Ti-26Nb-1Si alloy were produced via conventional powder metallurgy route by applying low pressure. The influence of TiH2 Powder addition on some physical and mechanical properties of samples was investigated. The amount of TiH2 powder was used in the range of 0-40 weight percent. The powders were firstly mixed for 3 hours and then compacted uniaxially under a pressure of 88 MPa. The green compacts were sintered at various temperatures between 800-1300 oC for 150 minutes. For evaluating the amounts of total and open porosities were determined by Archimedes principle. The porosity morphology and microstructures of specimens were examined using optical and electron microscopy. The formed phases were identified with X-ray diffraction method. The hardness test and compression test were carried out to compare these mechanical properties of different specimens. Bioactivity of specimens was examined with immersion in Stimulated Body Fluids (SBF) at 36.5 oC for 28 days. Referring to results, the increasing of sintering temperature and amount of TiH2 in pure and alloyed specimens leads to decrease in the amount of total porosity, the size and interconnectivity of pores decrease. The specimens with more amount of TiH2 contain finer α and βlayers. Results of SEM and EDS of immersed specimens in SBF show that presence of pores increases bioactivity of titanium specimens. Globular aggregates of hydroxyapatite (HA) with ratio of (Ca/P) 1.53 are created in pores after immersion in SBF for 28 days. Compression test results showed that increasing temperature and amount of TiH2 cause to increasing of elastic modulus and yield strength. Considering proposed yield strength values for implants, the optimum condition corresponds to 40 wt.% TiH2 and sintering temperature above of 900 oC for pure specimens. This matches with 20 and 40 wt.% TiH2 and sintering temperature above of 900 oC for alloyed specimens.

  9. Keywords:
  10. Titanium ; Powder Metallurgy ; Bioactivity ; Mechanical Alloying ; Titanium Hydride ; Elastic Modulus ; Porous Product

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