Loading...

Effect of Grain Refining, Cooling Rate and Modification on Shrinkage Porosities in A356 Aluminum Alloy

Hajizadeh Bidgoli, Ali | 2017

601 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50015 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Varahram, Naser
  7. Abstract:
  8. In this study, the influence of eutectic modification, grain refining and cooling rate on amount of shrinkage porosity in aluminium A356 alloy were investigated. Modification process for changing the morphology of eutectic silicon from needle like to fibrous like, use in aluminium – silicon alloys. This process often leads to increasing porosity in melt and affect harmfully on mechanical properties. For studying shrinkage porosity, the melt degassed completely to minimizing amount of gas in the melt. For modification, strontium in Al-10Sr master alloy and sodium in NaF salt used and for grain refining Al-10Ti and Al-5Ti-1B master alloys used. To study the effect of cooling rate, three mold with various internal diameter (15, 35 and 55 mm) and constant thickness (20 mm) were used. In other modes of experiment, one of the mold (35 mm internal diameter) were preheated before casting.samples were investigated with Archimedes test to determine the amount of porosity, hardness testing, metallography and scanning electron microscopy. The results showed that grain refining along with modification, decreases the amount of shrinkage porosity than samples that only modified. Increasing cooling rate also decreased the amount of shrinkage porosity. Hardness testing showed relative increase hardness in samples that grain refined and modified than samples that only modified. SEM analysis showed that porosity is shrinkage type and EDS analysis in the region near the porosity showed aluminium and silicon elements only. So there was no trace of other elements that could form intermetallic compound and modifier or grain refiner rich compound
  9. Keywords:
  10. Shrinkage Porosity ; Cooling Rate ; Modification ; Aluminum Alloy A356 ; Grain Refining

 Digital Object List

 Bookmark

No TOC