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A Study on the Thermal Stability and Microstructure of Nanocrystalline Al-Ti(Ni) Alloys Synthesized by Mechanical Alloying

Motaharinejad, Ruhollah | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40617 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Maddah Hosseini, Hamid Reza; Seyyed Reihani, Morteza
  7. Abstract:
  8. In the present investigation, the mechanical alloying (MA) technique was employed to produce nanocrystalline Al-Ti Powder mixtures. Elemental Al and Ti powders were mixed with different compositions (0, 5, 10, and 20 wt.% Ti) and then, milled in a vibratory mill up to 7 hr. The variations of powder morphology and particle size, apparent and tap densities, microstructure, grain size, lattice strain, and microhardness were studied with increasing the milling time. While dissolution of Ti in the Al matrix resulted to the formation of supersaturated Al-Ti solid solution in the samples containing 5 and 10 wt.% Ti, the specimen with 20 wt.% Ti, eventually, led to nanocomposite powder with different types of intermetallic reinforcements, at the end of milling operation. The grain size of all samples tended to the values of lower than 50 nm. The changes in apparent and tap densities were found to be in accordance with morphological evolution during the MA process. In addition, Thermal stability and phase transformation were studied through DTA and XRD tests for powders subjected to 350, 450, 550oC during 1 hr, the grain growth results depicted no grains grater than 100nm.
  9. Keywords:
  10. Aluminum Matrix Nanocomposite ; Mechanical Alloying ; Thermal Stability ; Grain Growth

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