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Study of Mechanical Properties of High Tempreture Al Nano-composites with Al2O3-Al3Ti based on theThermal Degradation of Aluminium Titanate

Lotfi, Nasrin | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53640 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Madaah Hosseini, Hamid Reza
  7. Abstract:
  8. In this study, in situ Al-Al3Ti-Al2O3 nanocomposite has been fabricated on thermal decomposition of tialite (Al2TiO5 or AT) precursor in the aluminum matrix through powder metallurgy method. The high-temperature mechanical property of Al-Al3Ti-Al2O3 on this procedure has been investigated. In the first step nano-structured tialite were synthesized through citrate sol-gel methods. Then 3.5 wt.% tialite powder was mixed with aluminum by high energy vibratory milling for 3 hours. In the next step, green compacts of mechanically milled powder mixtures were sintered at 530°С for 6 hours under argon atmosphere. In the final step, hot extrusion as a consolidation method reduces the sample voids, increases the density, and causes to redistribution of reinforcement. Because of sample preheating at 530°С for 90 minutes, tialite decomposed completely and at the end, fully dense samples were obtained. Samples were studied precise and comprehensive by optical microscope, field emission scanning electron microscope, X-ray diffraction, macro and micro hardness, and hot tensile tests. Finally, to investigate the mechanical properties of high temperature and the effect of sintering on the produced composite, sintered and non-sintered samples at temperatures of 200 °С, 300 °С and 400 °С with strain rates of 10-3 s-1, 5×10-3 s-1, and 10-2 s-1 Hot tensile test was performed. The hardness of nanocomposites increased to 47.6 HV before extrusion and to 94.1 HV after hot extrusion. The fracture surfaces of tested samples are characterized by mixed modes of ductile (dimple formation) and brittle (cleavage) failures, which were dependent on the deformation conditions of temperature and strain rate
  9. Keywords:
  10. Hot Extrusion ; Warm Tension Test ; Mechanical Properties ; In-Situ Nanocomposite ; Aluminum Matrix Nanocomposite ; High-Tempreture Mechanical Property

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