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Mechanical Property and Structural Changes of Pure Magnesium and AZ91 Alloy Using ECAP Process

Garmroodi, Peiman | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54224 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Assempour, Ahmad
  7. Abstract:
  8. In recent years, severe plastic deformation processes have been widely used to correct the grain size of metals. One of these methods is equal channel angular pressing. In this research, the improvement of mechanical property and structural changes of pure magnesium and AZ91 alloy after the ECAP process are investigated. The mold is made of H13 steel with a 90-degree channel crossing angle and a zero-degree external curve angle. The purpose of this study is to find the smallest average grain size at the optimum temperature on these materials. First, pure magnesium and AZ91 are subjected to the ECAP process at temperatures of 250, 300, 350, and 400 °C to calculate the best operating temperature in terms of grain size, and then the effect of pass numbers of these materials is investigated. The microstructure of the material is examined using an optical microscope and the mechanical properties are examined using a microhardness test. the smallest average grain size for pure magnesium is achieved at 250 ° C which was 6 microns. The results of AZ91 magnesium alloy show the best temperature at 300 ° C with a grain size of 3 microns. Then, by increasing the number of passes on this material, the grain size decreases to 2 microns. Metallographic images indicate the occurrence of dynamic recrystallization in all samples. The Micro-hardness test on the AZ91 alloy samples shows that the ECAP process improves the hardness of the material at temperatures of 300 and 350 ° C and in the best case the hardness of the material reaches from 66 to 87 Vickers. Also, by increasing the number of passes on magnesium, a more homogeneous structure is obtained
  9. Keywords:
  10. Magnesium ; Severe Plastic Deformation ; Equal Channel Angular Pressing (ECAP) ; AZ91 Magnesium Alloy ; Fine Grain Material

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