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Effect Of Mechanical Milling on the Microstructure Development and Mechanical Properties of Gas-Atomized Al-20Si-5Fe-2Ni Alloy

Karimi, Manoochehr | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42351 (07)
  4. University: Sharif University of Technology
  5. Department: Materials science and Engineering
  6. Advisor(s): Simchi, Abdolreza; Maddah Hosseini, Hamid Reza
  7. Abstract:
  8. In this work, hypereutectic Al-20Si-5Fe-2Ni powder was prepared by gas atomizing method. The alloy was fabricated by melting of commercially pure metals and re-melting at approximately 200 K above the liquidus temperature. The molten alloy was then atomized by nitrogen at a gas pressure of 0.8 MPa. The nozzle diameter was 3 mm. The aluminum alloy powders were milled under pure Argon atmosphere with a ball to powder ratio of 10:1 in a planetary ball for 12, 24, 36 and 48 hours. The gas-atomized and milled powders were then consolidated by cold sintering method. Microstructure and phase analysis were performed by SEM and XRD technique. Mechanical properties were evaluated by microhardness and compression tests. Microstructure of atomized powder consisted of particle-like primary Si with average diameter of 0.5–2.7 µm, δ-Al4FeSi2 intermetallic phase with the size of 1.4–7.7 µm, and fine Al–Si eutectic matrix with 0.25–0.4 µm spacing. The intermetallic phase was broken during the milling and crystallite size decreased to 40 nm. Microhardness and compression test results show that hardness and strength increased by 18 and 30 percent during milling, respectively.In this work, hypereutectic Al-20Si-5Fe-2Ni powder was prepared by gas atomizing method. The alloy was fabricated by melting of commercially pure metals and re-melting at approximately 200 K above the liquidus temperature. The molten alloy was then atomized by nitrogen at a gas pressure of 0.8 MPa. The nozzle diameter was 3 mm. The aluminum alloy powders were milled under pure Argon atmosphere with a ball to powder ratio of 10:1 in a planetary ball for 12, 24, 36 and 48 hours. The gas-atomized and milled powders were then consolidated by cold sintering method. Microstructure and phase analysis were performed by SEM and XRD technique. Mechanical properties were evaluated by microhardness and compression tests. Microstructure of atomized powder consisted of particle-like primary Si with average diameter of 0.5–2.7 µm, δ-Al4FeSi2 intermetallic phase with the size of 1.4–7.7 µm, and fine Al–Si eutectic matrix with 0.25–0.4 µm spacing. The intermetallic phase was broken during the milling and crystallite size decreased to 40 nm. Microhardness and compression test results show that hardness and strength increased by 18 and 30 percent during milling, respectively
  9. Keywords:
  10. Mechanical Milling ; Rapid Solidification ; Mechanical Properties ; Nanostructure ; Cold Sintering

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