The effects of Mg content and cooling rate on the solidification behaviour of Al-7%Si-Mg（mass fraction） casting alloys have been investigated using differential scanning calorimetry, differential thermal analysis an...The effects of Mg content and cooling rate on the solidification behaviour of Al-7%Si-Mg（mass fraction） casting alloys have been investigated using differential scanning calorimetry, differential thermal analysis and microscopy. The Mg contents were selected as respectively 0.00%, 0.35% and 0.70%（mass fraction）. DTA curves of Al-7%Si-0.55%Mg（mass fraction） alloy at various cooling rates were accomplished and the alloy melt was cast in different cooling rates. The results indicate that increasing Mg content can lower the liquidus and binary Al-Si eutectic transformation temperatures. Large Fe-rich π-phases （Al8FeMg3Si6） are found in the 0.70% Mg alloys together with some small β-phases （Al5FeSi）; in contrast, only β-phases are observed in the 0.35% Mg alloys. The test results of the Al-7%Si-0.55%Mg alloys identify that the liquidus and binary Al-Si eutectic transformation temperatures decrease, and the quantity of ternary Al-Si-Mg2Si eutectic phase decreases as the cooling rate increases.展开更多
Ethylene tar pitch was co-carbonized with waste polystyrene to prepare mesophase pitch. The character- istics of mesophase pitches were examined using polarized light optical microscopy, apparent viscome- try, Fourier...Ethylene tar pitch was co-carbonized with waste polystyrene to prepare mesophase pitch. The character- istics of mesophase pitches were examined using polarized light optical microscopy, apparent viscome- try, Fourier transform infrared spectrometry, IH nuclear magnetic resonance spectrometry, and X-ray diffractometry. The properties of the mesophase pitch were greatly improved because of the eutectic effect. The soluble content increased from 5% to 56%, the mesophase itself increased from 32% to 100%, and the optical texture was changed from a coarse mosaic into a flow domain after the waste polystyrene was added to the ethylene tar pitch. The apparent viscosity showed that the mesophase pitch changed from thixotropic to Newtonian suggesting improved rheological behavior during co-carbonization）The increased number of alkyl groups, which are mainly methylene groups, altered the molecular structure of the mesophase pitch in a way that resulted in the eutectic effect.展开更多
基金Project (G2000067202) supported by the National Major Basic Research Program of China
文摘The effects of Mg content and cooling rate on the solidification behaviour of Al-7%Si-Mg（mass fraction） casting alloys have been investigated using differential scanning calorimetry, differential thermal analysis and microscopy. The Mg contents were selected as respectively 0.00%, 0.35% and 0.70%（mass fraction）. DTA curves of Al-7%Si-0.55%Mg（mass fraction） alloy at various cooling rates were accomplished and the alloy melt was cast in different cooling rates. The results indicate that increasing Mg content can lower the liquidus and binary Al-Si eutectic transformation temperatures. Large Fe-rich π-phases （Al8FeMg3Si6） are found in the 0.70% Mg alloys together with some small β-phases （Al5FeSi）; in contrast, only β-phases are observed in the 0.35% Mg alloys. The test results of the Al-7%Si-0.55%Mg alloys identify that the liquidus and binary Al-Si eutectic transformation temperatures decrease, and the quantity of ternary Al-Si-Mg2Si eutectic phase decreases as the cooling rate increases.
基金the financial support by the Fundamental Research Funds for the Central Universities (No.2010QNA14)
文摘Ethylene tar pitch was co-carbonized with waste polystyrene to prepare mesophase pitch. The character- istics of mesophase pitches were examined using polarized light optical microscopy, apparent viscome- try, Fourier transform infrared spectrometry, IH nuclear magnetic resonance spectrometry, and X-ray diffractometry. The properties of the mesophase pitch were greatly improved because of the eutectic effect. The soluble content increased from 5% to 56%, the mesophase itself increased from 32% to 100%, and the optical texture was changed from a coarse mosaic into a flow domain after the waste polystyrene was added to the ethylene tar pitch. The apparent viscosity showed that the mesophase pitch changed from thixotropic to Newtonian suggesting improved rheological behavior during co-carbonization）The increased number of alkyl groups, which are mainly methylene groups, altered the molecular structure of the mesophase pitch in a way that resulted in the eutectic effect.
