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An Investigation into the Microstructure and Mechanical Properties of Rheoforged A356 Alloy After Severe Plastic Deformation

Dodangeh, Abbas | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43416 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen; Aashuri, Hossein
  7. Abstract:
  8. Several studies are already on severe plastic deformation of wrought and cast aluminum alloys. Among these studies, no evidence of applying severe plastic deformation on the structure of rheocast or rheoforgedaluminum alloy can be found. So, in this research A356 alloy with globular structure was achieved using electromagnetic stirring and rheoforging. The optimum condition of globular structure with high sphericity was achievedafter holding the produced structure in semi-solid state for 10 min. Then, the effect of severe plastic deformation on mechanical and microstructural properties of this alloy and cast alloy was studied. The results show that with applying 3 passes of multidirectional forging (MDF) to the globular structure, without a significant change in the mean shape factor of the globules, the maximum increase in hardness and shear strength of the alloys are 61 and 25 percent,respectively. For the cast alloy, after applying 1 pass of MDF, hardness and shear strength of the alloy was increased about 38 percent. Also, the results indicate the SIMA process on cast structure led toglobular structure with smaller globule sizein comparison with the rheoforged sample holden at semi solid temperature. In the next step, the effect of aging heat treatment at 200°C for different timeson the globular sample in three different modes: aging without plastic deformation, plastic deformation before aging and plastic deformation after aging was studied. In the case of the aged sample without plastic deformation, maximum hardness of 103 Vickers was achievedin 120 minutes. Maximum hardness of 110 Vickers was achieved in 60 minutes in the sample that aged before applying strain. The results of aging treatment show that applying the aging after plastic deformation reduced the time of reaching to the maximum hardness (103 vickers in 8 minutes).
  9. Keywords:
  10. Mechanical Properties ; Microstructure ; Aluminum Alloy A356 ; Severe Plastic Deformation ; Rheoforge

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