Loading...

Correlation Between Mechanical Properties and Microstructure Evolution of Al / Al2O3-Al3Ti-CNT Hybrid Nanocomposites Produced by Plasma Plasma Sintering (SPS) based on Thermal Decomposition of Aluminum Titanate Nanostructure

Azarniya, Abolfazl | 2022

192 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55083 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Madaah Hosseini, Hamid Reza; Ramakrishna, Seeram
  7. Abstract:
  8. In this research, aluminum titanate or tialite with the chemical composition of Al2TiO5 was synthesized as nanostructured form using the sol-gel method with the aim to serve as a chemical source for aluminum and titanium elements within the fabrication of in-situ Al2O3-Al3Ti-reinforced aluminum matrix nanocomposites. Since the aforementioned nanocomposite is produced based on the thermal decomposition of tialite, the thermar decomposition of this material in air atmosphere, under applied mechanical strain, and direct contact with the underlying aluminum was comprehensively evaluated. The empirical results showed that as tialite is exposed to aluminium, the reaction starts from low temperatures (about 200 ° C) and ends up to about 600 ° C. The byproducts of this decomposition include Al2O3 and AlxTiy phases with different stoichiometric ratios (such as Al3Ti, Al2Ti, AlTi, AlTi3, and Al5Ti2). Since the related reactions may produce large content of oxygen gas, it can lead to structural porosity when used in a compacted powder system. To prevent this undesirable phenomenon, the reaction between aluminum and tialite was performed in powder form, aimed at easily relealsing oxygen gas into the environment and keeping the remaining mixture free of any detrimental agents. The powder product left from this reaction has been referred to as "black powder" in the present study. To fabricate hybrid in-situ composites, 10 weight percent of black powder and 5 weight percent of carbon microfibers were added to the aluminum matrix using the mechanical alloying and compacted by plasma plasma sintering (SPS). The resulting nanocomposite bore a hierarchical and multiscale microstructure, consisting of reinforcing particles, Al4C3, TiC, Al3Ti, Al2O3, Al4O4C, and Ti3AlC. The mechanical compressive strength of the hybrid composites were evaluated, where the obtained results indicated that this strengthening was able to increase the maximum compressive strength from 300 MPa for pure aluminum to 400 MPa, while the final composite has a fracture strain of about 23% The strengthening mechanism arisen from the increased density of dislocations is the most effective mechanism in these composites, followed by the Orowan and grain refinement mechanisms, respectively as the further most effective ones
  9. Keywords:
  10. Metal Matrix Nanocomposite ; Mechanical Properties ; Phase Transformation ; Strengthening (Metal) ; Phase Characterization ; In-Situ Nanocomposite ; Spark Plasma Sintering

 Digital Object List

 Bookmark

No TOC