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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 40454 (07)
- University: Sharif University of Technology
- Department: Materials Science and Engineering
- Advisor(s): Ashuri, Hossein
- Abstract:
- Hypereutectic A390 alloy has some exclusive specification among aluminum alloys because of its' excellent properties such as high wear resistance and low thermal expansion. In this research powder-thixoforming method, a compilation of powder and thixoforming methods is used for production of parts. In this method gas atomized powder of pre-fabricated alloy was consolidated by hot pressing under argon atmosphere and converted to an acceptable feedstock for thixoforming stage. The feedstock is reheated to semi solid region and rapidly transferred to a injection sleeve with central runner. The semi-solid feedstock is injected in a step die by a hydraulic press of 1 m/s ram speed. According to the obtained results, formation of continuous eutectic melt containing copper and melting the α-Al dendritic germs existing in the structure seem to be the dominate mechanism for sphering the particles. In this state with continuing to hold in semi solid temperature, the α-Al globules are grown by Ostwald ripening and coalescence and create final globular structure. Also Si eutectic particles reach to primary Si by diffusion through of α-Al globules and melt phase and cause growth of primary Si
- Keywords:
- Aluminum Alloy A390 ; Thixoforming ; Semi-Solid Processing ; Hot Press ; Gas Atomization ; Hypereutectic Aluminum-Silicon-Ferrite ; Powder Consolidation
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محتواي پايان نامه
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