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Using FSP Method to Create Composite and Surface Foam with Distribution Gradient of Particles and Porosity as FGM and Study of Physical and Mechanical Properties

Karimi, Mahdi | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53419 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Akbarzadeh, Abbas
  7. Abstract:
  8. Nowadays, the tendency to use Al/SiC composites with FGM structure has increased in the automotive and aerospace industries, because in this type of composite, the properties can be gradually changed in the direction of thickness. For example, one composite surface is used as a wear-resistant or high-temperature-resistant coating, and the other surface can be welded, has high thermal conductivity, or has a good toughness. In recent years, methods have been used to make surface composites, most of which are in the molten state and at high temperatures. In this case, the reactions between the compounds can not be easily controlled and the possibility of the formation of undesirable or intermetallic phases during freezing is very high. In this study, with the help of controlling FSP process variables and design factors, Al/SiC composite with FGM gradient structure was fabricated in which the percentage of SiC powder from zero percent in the center of the sample reaches about 16 percent at its surface. The results show that the use of Fluted Frustum pin with rotational speed of 800 rpm and transfer speed of 60 mm/min provides the best conditions in terms of the absence of defects in the FSP structure and in addition, causes a favorable distribution of SiC particles in the composite field and makes it possible to reach the FGM structure. It was shown that the FG-Al/SiC composite made by friction stir method has an abrasion coefficient of about 35% and a friction coefficient of about٪ 20 lower than the original commercial pure aluminum in 1000 m slip distance. This composite increased the hardness of the base metal from 20 to 50 Vickers and the strength from 66 MPa to 116 MPa and only reduced the elongation rate by 14%. A foam gradient structure was created by the preparation of FG-Al TiH2 composite with FSP method and decomposition of TiH2 particle by appropriate heat treatment. The results showed that the distribution of TiH2 particles had a more uniform distribution than SiC due to its larger size and this proper distribution creates a zero to 28% porosity gradient from the center of the sample to its surface after heat treatment
  9. Keywords:
  10. Aluminum Matrix Composite ; Metal Foam ; Functionally Graded Materials (FGM) ; Metal Matrix Composite (MMC) ; Friction Stir Processing ; Friction Stir Welding ; Silicon Carbide ; Titanium Hydride

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