Optical microscope and SEM were used to observe the changes of the microstructure of Al 11.6% Si 0.4% Mg alloys with varying strontium additions and the effect of strontium on the crystallization of Mg 2Si phase was d...Optical microscope and SEM were used to observe the changes of the microstructure of Al 11.6% Si 0.4% Mg alloys with varying strontium additions and the effect of strontium on the crystallization of Mg 2Si phase was discussed. It is found that Mg 2Si phase nucleates on the surfaces of the eutectic silicon flakes in the unfully modified alloys, growing as meshwork or bamboo shoot shape, however, very few and fine Mg 2Si particles phase are isolated at the boundaries of the eutectic cells in the fully modified alloys. Strontium has an important influence on the crystallization of Mg 2Si phase in Al Si Mg casting alloys and it is thought to be related to the increase of the amount of dendritic α phase and the modifying degree of eutectic silicon phase.展开更多
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
文摘Optical microscope and SEM were used to observe the changes of the microstructure of Al 11.6% Si 0.4% Mg alloys with varying strontium additions and the effect of strontium on the crystallization of Mg 2Si phase was discussed. It is found that Mg 2Si phase nucleates on the surfaces of the eutectic silicon flakes in the unfully modified alloys, growing as meshwork or bamboo shoot shape, however, very few and fine Mg 2Si particles phase are isolated at the boundaries of the eutectic cells in the fully modified alloys. Strontium has an important influence on the crystallization of Mg 2Si phase in Al Si Mg casting alloys and it is thought to be related to the increase of the amount of dendritic α phase and the modifying degree of eutectic silicon phase.
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.
