Solidification process of A357 alloy with Sr addition was investigated in this paper.In particular,the effects of strontium and cooling rate on α-Al dendrite and Al-Si eutectic characteristic temperature were charact...Solidification process of A357 alloy with Sr addition was investigated in this paper.In particular,the effects of strontium and cooling rate on α-Al dendrite and Al-Si eutectic characteristic temperature were characterized by differential thermal analysis(DTA).Sr addition not only modifies the Al-Si eutectic,but also affects the morphology and structure of primary α-Al dendrite.Sr decreases the growth temperature of α-Al dendrite and Al-Si eutectic,and it also affects the dendrite growth mechanism.It has been found that such effect becomes more significant with higher cooling rate.展开更多
The effects of different cooling conditions on the mechanical properties and microstructures of a Sr-modified A356 （Al-7Si-0.3Mg） aluminum casting alloy were comparatively investigated using three moulding sands inc...The effects of different cooling conditions on the mechanical properties and microstructures of a Sr-modified A356 （Al-7Si-0.3Mg） aluminum casting alloy were comparatively investigated using three moulding sands including quartz, alumina and chromite into multi-step blocks. The results show that the mechanical properties and microstructures using chromite sand are the best. As the cooling speed increases, the dendrite arm spacing （DAS） decreases significantly and the mechanical properties are improved, and the elongation is more sensitive to the cooling speed as compared with the tensile strength. The increase of the properties is primarily attributed to the decrease of the DAS and the increase of the free strontium atoms in the matrix. In particular, the regression models for predicting both the tensile strength and the elongation for Sr-modified A356 aluminum casting alloy were established based on the experimental data.展开更多
Many investigations have revealed that transition of melt structure can effectively influence the final solidification microstructures. In this study, ultrasonic treatment was applied to AI-20%Si melt and Sr-modified ...Many investigations have revealed that transition of melt structure can effectively influence the final solidification microstructures. In this study, ultrasonic treatment was applied to AI-20%Si melt and Sr-modified AI-20%Si melt at 720 ℃ （i.e. above liquidus of about 690℃） for 60 s, and then the melt was quickly quenched to room temperature. Experimental results show that ultrasonic treatment can refine the primary Si phase and a-AI of AI-20%Si alloy; strontium can make the morphology of Si phase spheroidized and refined as Sr addition changes the faceted growth characteristic of Si phase; however, the refinement effect of ultrasonic treatment on the primary Si phase and α-AI is weakened by Sr addition.展开更多
基金supported by the Natural Science Fund of Shanxi Province (No. SJ08-ZT05) Open Research Fund of Shenzhen Key Laboratory of Special Functional Materials,Shenzhen University (No. 2T0804)
文摘Solidification process of A357 alloy with Sr addition was investigated in this paper.In particular,the effects of strontium and cooling rate on α-Al dendrite and Al-Si eutectic characteristic temperature were characterized by differential thermal analysis(DTA).Sr addition not only modifies the Al-Si eutectic,but also affects the morphology and structure of primary α-Al dendrite.Sr decreases the growth temperature of α-Al dendrite and Al-Si eutectic,and it also affects the dendrite growth mechanism.It has been found that such effect becomes more significant with higher cooling rate.
基金Project (50971087) supported by the National Natural Science Foundation of ChinaProject (11JDG070) supported by the Senior Talent Research Foundation of Jiangsu University, China
文摘The effects of different cooling conditions on the mechanical properties and microstructures of a Sr-modified A356 （Al-7Si-0.3Mg） aluminum casting alloy were comparatively investigated using three moulding sands including quartz, alumina and chromite into multi-step blocks. The results show that the mechanical properties and microstructures using chromite sand are the best. As the cooling speed increases, the dendrite arm spacing （DAS） decreases significantly and the mechanical properties are improved, and the elongation is more sensitive to the cooling speed as compared with the tensile strength. The increase of the properties is primarily attributed to the decrease of the DAS and the increase of the free strontium atoms in the matrix. In particular, the regression models for predicting both the tensile strength and the elongation for Sr-modified A356 aluminum casting alloy were established based on the experimental data.
基金financially supported by the National Natural Science Foundation of China under contract No.50874022
文摘Many investigations have revealed that transition of melt structure can effectively influence the final solidification microstructures. In this study, ultrasonic treatment was applied to AI-20%Si melt and Sr-modified AI-20%Si melt at 720 ℃ （i.e. above liquidus of about 690℃） for 60 s, and then the melt was quickly quenched to room temperature. Experimental results show that ultrasonic treatment can refine the primary Si phase and a-AI of AI-20%Si alloy; strontium can make the morphology of Si phase spheroidized and refined as Sr addition changes the faceted growth characteristic of Si phase; however, the refinement effect of ultrasonic treatment on the primary Si phase and α-AI is weakened by Sr addition.
