Iron （Fe） has a low solid solubility in aluminum （Al）, and it usually forms Fe-rich intermetallic compounds. Scandium （Sc） is an element that can act as a grain refiner, modify the eutectic silicon and change th...Iron （Fe） has a low solid solubility in aluminum （Al）, and it usually forms Fe-rich intermetallic compounds. Scandium （Sc） is an element that can act as a grain refiner, modify the eutectic silicon and change the morphology of Fe-rich intermetallic compounds at the same time. The present work was conducted to study the effect of Sc on the mechanical properties of Al-7Si-0.3Mg. The alloy was prepared by squeeze casting at two levels of Fe （0.2 and 0.4 wt%） and three levels of Sc （0 wt%, 0.2 wt% and 0.4 wt%）. Sc is found to increase the mechanical properties of the alloy, including its hardness, yield strength and ultimate tensile strength. At 0.2 wt% Fe, adding Sc increases the strength while maintaining good elongation. At 0.4 wt% Fe, adding Sc increases the strength but decreases the elongation slightly. The distributions and morphologies of intermetallic compounds and eutectic silicon affect the elongation. Both Fe-rich intermetallic compounds and Sc-rich intermetallic compounds act as crack initiation sites. The 0.2 wt% Fe ＋ 0.2 wt% Sc alloy has the lowest amount of these intermetallic compounds, and eutectic silicon is small and fibrous. So, it has the highest elongation.展开更多
The effects of erbium addition on the rheological properties and microstructure of a semisolid A356 alloy were studied.The semisolid slurries were prepared through the serpentine channel technique before they were thi...The effects of erbium addition on the rheological properties and microstructure of a semisolid A356 alloy were studied.The semisolid slurries were prepared through the serpentine channel technique before they were thixoformed using parallel-plate compre ssion with cylindrical discs.The grain and globule size decreases as the Er content increases,resulting in an improved and uniform distribution of spherical primaryα-Al phase within the semisolid slurry.The addition of the Er modifies the grain morphology and size of theα-Al grains,resulting in a better and more uniform distribution of spherical primaryα-AI phase within the semisolid slurry.As a result,rheocast quality index increases with the addition of Er,which is suitable for the thixoforming process.The A356 alloy without Er has the highest viscosity herein.The viscosity decreases,and the flow characteristics of the semisolid feedstock are expected to improve when Er is added as a result of the refinement of primary a-Al and modification of eutectic silicon.Furthermore,the refined semisolid A356 alloys with Er show a slightly larger fraction of highangle grain boundaries compared to that for the unrefined alloy.展开更多
基金financially supported by the Royal Golden Jubilee Ph.D.Program (No.PHD/0285/2552)the King Mongkut's University of Technology Thonburi,National Metal and Materials Technology Center (No.MT-B-58-MET-07-265-I)
文摘Iron （Fe） has a low solid solubility in aluminum （Al）, and it usually forms Fe-rich intermetallic compounds. Scandium （Sc） is an element that can act as a grain refiner, modify the eutectic silicon and change the morphology of Fe-rich intermetallic compounds at the same time. The present work was conducted to study the effect of Sc on the mechanical properties of Al-7Si-0.3Mg. The alloy was prepared by squeeze casting at two levels of Fe （0.2 and 0.4 wt%） and three levels of Sc （0 wt%, 0.2 wt% and 0.4 wt%）. Sc is found to increase the mechanical properties of the alloy, including its hardness, yield strength and ultimate tensile strength. At 0.2 wt% Fe, adding Sc increases the strength while maintaining good elongation. At 0.4 wt% Fe, adding Sc increases the strength but decreases the elongation slightly. The distributions and morphologies of intermetallic compounds and eutectic silicon affect the elongation. Both Fe-rich intermetallic compounds and Sc-rich intermetallic compounds act as crack initiation sites. The 0.2 wt% Fe ＋ 0.2 wt% Sc alloy has the lowest amount of these intermetallic compounds, and eutectic silicon is small and fibrous. So, it has the highest elongation.
文摘The effects of erbium addition on the rheological properties and microstructure of a semisolid A356 alloy were studied.The semisolid slurries were prepared through the serpentine channel technique before they were thixoformed using parallel-plate compre ssion with cylindrical discs.The grain and globule size decreases as the Er content increases,resulting in an improved and uniform distribution of spherical primaryα-Al phase within the semisolid slurry.The addition of the Er modifies the grain morphology and size of theα-Al grains,resulting in a better and more uniform distribution of spherical primaryα-AI phase within the semisolid slurry.As a result,rheocast quality index increases with the addition of Er,which is suitable for the thixoforming process.The A356 alloy without Er has the highest viscosity herein.The viscosity decreases,and the flow characteristics of the semisolid feedstock are expected to improve when Er is added as a result of the refinement of primary a-Al and modification of eutectic silicon.Furthermore,the refined semisolid A356 alloys with Er show a slightly larger fraction of highangle grain boundaries compared to that for the unrefined alloy.
