Loading...

Investigation on the Effect of Cooling Rate on the Solidification Behavior and Microstructure of Al 713 alloy using Thermal Analysis Technique

Abbasi, Mohammad Hossein | 2016

696 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48455 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Varahram, Nasser
  7. Abstract:
  8. Considering the limited number of works on investigation of solidification characteristics of Al-Zn-Mg-Cu cast alloys as well as the applications of this alloy system in aerospace industries, the solidification conditions of Al 713 alloy were investigated in this study. In order to achieve this goal, a number of experiments were designed and conducted including quantometry, thermal analysis, metallography and hardness measurements. In this thesis, effects of cooling rate on secondary dendritic arms spacing as well as solidification parameters including nucleation temperature, solidification time and temperature range, dendrite coherency point and formation temperature of intermetallic compounds during the solidification of alloy were investigated. To obtain various cooling rates, different dies made of CO2 sand, ceramics, stainless steel with thicknesses of 5 and 10 mm, H13 hot-work steel and copper were employed. Computer-aided thermal analysis was used to calculate cooling rates as well as solidification parameters, and cooling rates in range of 0.13 to 0.87°C/s were resulted. Microstructural studies were done using optical microscopy along with the CLEMEX software. It was observed that by increase in the cooling rate from 0.13 to 0.87°C/s, the secondary dendritic arms spacing (SDAS) was decreased by 55%. Enhancement of cooling rate led to decrease in nucleation temperature as well as increase in solidification time. It was also observed that both time and temperature ranges of solidification were decreased by increase in the cooling rate. Then, the mathematical relationship between the cooling rate and secondary dendritic arms spacing as well as cooling curve parameters including nucleation temperature, solidification time and time and temperature ranges of solidification was determined. In addition, in order to investigate the effect of cooling rate on characteristics of dendrite coherency point, thermal analysis experiments were conducted at various solidification conditions using two thermocouples, and the optimum coherency conditions of Al 713 alloy were determined. Equilibrium phases present in the Al 713 microstructure were determined by thermodynamical simulations using ProCast as well as microstructural observations by SEM/EDS, and effect of cooling rate on formation of intermetallic compounds in the solidification temperature range was obtained by thermal analysis method.
  9. Keywords:
  10. Cooling Rate ; Solidification Time ; Intermetallic Compounds ; Dendrite Arm Space (DAS) ; Thermal Analysis ; Secondary Dendrite Arm Spacing (SDAS) ; Aluminum Alloy 713

 Digital Object List

 Bookmark

No TOC