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An Investigation of Strain, Temperature Distribution and Mechanical Properties of Product in Hot Extrusion of AA7075

Imenabadi, Amir | 2008

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39119 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali
  7. Abstract:
  8. More than 70% of the components used in aerospace, aircraft and defence industries Are made of aluminum alloys. The 7xxx series of Al alloys such as AA7075 and AA7175 are typical alloys utilized in the mentioned industries. For these alloys, the optimization of the extrusion process in term of reaching a maximum extrusion quality without jeoparding the extrudate, the surface and microstructural properties is far more complex than other aluminum alloys. It is generally accepted that product properties are closely correlated to microstructure. So it is of paramount importance to understand the way in which the structure is modified and how the forming parameters i.e. temperature, ram speed, and die geometry affect these modifications. In this study the effect of die geometry and extrusion parameters on strain and temperature distribution on metal flow and mechanical properties of extrudate is investigated. The theoretical and experimental results indicated that die profile has a significant influence on stain and temperature inhomogeniety in extrusion product. Convex elliptic die profile, as the result of high strain rate distribution, produces the maximum temperature of extrudate. In conical die, the redundant strain yields the most inhomogenity. Initial temperature of billet and reduction affect on temperature and strain field and also mechanical behavior, so that increasing the initial temperature and reduction increase the maximum temperature. It was shown that extrusion load is affected by die profile and other forming parameters. The maximum extrusion load belongs to conical die and the minimum one belongs to cosine die profile. Moreover, it was shown that increasing in temperature and reduction reduce the extrusion load
  9. Keywords:
  10. Modeling ; Hot Extrusion ; Upper Bound Method ; Die Profile ; Aluminum Alloy 7075 ; Inhomogeneous Deformation

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