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Fabrication & Characterization of Al-Al3Ti-Al2O3 Nano-composites Based on the Thermal Degradation of Aluminium Titanate & Facile Study on the Correlation between Microstructure & Their Mechanical Properties

Ahmadvand, Mohammad Saeed | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50578 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Maddah Hosseini, Hamid Reza
  7. Abstract:
  8. In this study insitu Al-Al3Ti-Al2O3 nanocomposite has been fabricated based on thermal decomposition of tialite (Al2TiO5) precursor in aluminium matrix through powder metallurgy method. Also the effect of high energy mechanical milling and hot extrusion on this procedure has been investigated. In the first step nano-structured tialite were synthesized through citrate sol gel methods. Then, different volume fraction of tialte was mixed with aluminium by high energy vibratory milling. The results of X-ray differaction analysis, scanning electron microscopy and differential thermal analysis showed that mechanical milling can degrade stability of tialite and cause strain-induced decomposition, improve the kinetic of reactions between aluminium and tialite through increase their interface, reduce the TiO2-Al reaction temperature from 600 oC to about 450oC and distribute homogenously nano-size tialte particles in equiaxed aluminium particles. In the next step, green compacts of mechanically milled powder mixtrures were sintered at 450 oC and 550 oC for 6 hours. Results of X-ray differaction analysis and field emission electron scanning microscopy showed that 4 hours mechanical milling with sintering, minimize unreacted tialite in mixture, eliminate micro cracks in microstructure and distribute Al3Ti and Al2O3 nanoparticles homogenously in aluminium matrix but as a result of particles work hardening and increase in their hardness the bulk did not consolidate desirablely and the sintering was imperfect. So the sintered compacts preheated for 1 hours at 535 oC and then extruded at this temperature. As a result, a dense insitu Al-Al3Ti-Al2O3 nanocomposite was fabricated. In order to evaluate nanocomposite mechanical properties, in the final step, micro-hardness test and nano-indentation test has been carried out. Accordingly, the hardness of the nanocomposites reached 143 HV and its elastic modulus reached 90 GPa which shows improve in mechanical properties compare to previous studies
  9. Keywords:
  10. Nanoindentation ; Hot Extrusion ; Mechanical Milling ; Tialite ; In-Situ Nanocomposite ; Aluminum Matrix Nanocomposite ; Mechanical Alloying

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