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Rafiei, Alieh | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41377 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Varahram, Naser; Davami, Parviz
  7. Abstract:
  8. Al-20Si-5Fe-3Cu-1Mg–xCr (X=0, X=1.5) ribbons were produced by melt-spinning technique at the rotating speed of 20 and 40 ms-1. The thickness of ribbons were 40 to 80 and 15 to 35 μm, respectively. The properties of as-melt spun and as-cast specimen were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-Ray diffractometry (XRD) and the microhardness method. It was found that at the air side of ribbons the microstructure was dendritic while at the wheel side it was featureless. The microstructure of ribbons at two rotating speed showed a homogenous distribution of Si particles embedded in an α-Al matrix. XRD investigations exhibited the absence of any intermetallic phase formation after melt-spinning. The rapid solidification has a significant influence on the microstructure of Al-20Si-5Fe-3Cu-1Mg–xCr (X=0, X=1.5) alloys. The particle size in the microstructure of the ribbon was too small in compare with those of in as-cast samples. So that, the average size of Si particles was 200 and 350 nm at the rotating speed of 40 and 20m/s. Furthermore, the microhardness of the aluminum matrix at the wheel side of as-melt spun ribbons was drastically increased. The microhardness values of as melt-spun ribbons were about 3 times higher than those of as-cast counterparts that is attributed to changes in the microstructure. The effect of Cr addition (in as-cast samples) was the change of morphology of intermetallic phases from needle-like to fine particles
  9. Keywords:
  10. Hypereutectic Aluminum-Silicon-Ferrite ; Melt Spinning ; Microstructure ; Microhardness

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