Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationshi...Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationship between the initial hydrogen content inthe melt and the refinement effect on the casting of hypereutectic aluminum-silicon alloy wasinvestigated. The experimental results show that the cooling rate, the hydrogen content and thegrain refinement effect are three interactive factors. When the hydrogen content is above 0.20mL/100 g and the cooling rate is lower than that in 50 mm-thick step, hydrogen dissolved in thealloy melt influences the grain refinement effect. With increasing the cooling rate, the criticalhydrogen content increases too. It is expected that much hydrogen in the melt make the netinterfacial energy larger than or equal to zero, resulting in the shielding of the particles AlPduring solidification and that the critical gas content is closely related to the critical radius ofembryo bubbles.展开更多
By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus add...By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.展开更多
For the wider applications,it is necessary to improve the ductility as well as the strength and wear-resistance of hypereutectic AlSi-Cu alloys,which are typical light-weight wear-resistant materials.An increase in th...For the wider applications,it is necessary to improve the ductility as well as the strength and wear-resistance of hypereutectic AlSi-Cu alloys,which are typical light-weight wear-resistant materials.An increase in the amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys,but leads to the poor strength and ductility.It is known that dual phase steels composed of hetero-structure have succeeded in bringing contradictory mechanical properties of high strength and ductility concurrently.In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance,ultrasonic irradiation of the molten metal during the solidification,which is called sono-solidification,was carried out from its molten state to just above the eutectic temperature.The sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure,which are,hard primary silicon particles,soft non-equilibrium a-Al phase and the eutectic region.Rheo-casting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk specimen.After the rheo-casting with modified sonosolidified slurry held for 45 s at 570 oC,the quantitative optical microscope observation exhibits that the microstructure is composed of 18area%of hard primary silicon particles and 57area%of soft a-Al phase.In contrast,there exist only 5 area%of primary silicon particles and no a-Al phase in rheo-cast specimen with normally solidified slurry.Hence the tensile tests of T6 treated rheo-cast specimens with modified sono-solidified slurry exhibit improved strength and 5%of elongation,regardless of having more than 3 times higher amounts of primary silicon particles compared to that of rheo-cast specimen with normally solidified slurry.展开更多
研究了A l-25%Si合金在半固态等温电磁搅拌条件下合金显微组织的变化行为.分别在580℃、600℃下等温搅拌0 m in、10 m in、20 m in和30 m in,实验结果显示:随着搅拌时间的增加,初生硅发生细化,尺寸明显变小且边角更加钝化,分布也更加均...研究了A l-25%Si合金在半固态等温电磁搅拌条件下合金显微组织的变化行为.分别在580℃、600℃下等温搅拌0 m in、10 m in、20 m in和30 m in,实验结果显示:随着搅拌时间的增加,初生硅发生细化,尺寸明显变小且边角更加钝化,分布也更加均匀;当搅拌时间超过20 m in后,初生硅尺寸变化不大,分布趋于均匀.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.50071028)the Natural Science Foundation of Shandong Province in China (No. Z2001F02)
文摘Dissolved hydrogen is harmful to mechanical properties of refinedhypereutectic aluminum-silicon alloys. In the present work, by using a stepped-form mold and thehydrogen-detecting instrument HYSCAN II, the relationship between the initial hydrogen content inthe melt and the refinement effect on the casting of hypereutectic aluminum-silicon alloy wasinvestigated. The experimental results show that the cooling rate, the hydrogen content and thegrain refinement effect are three interactive factors. When the hydrogen content is above 0.20mL/100 g and the cooling rate is lower than that in 50 mm-thick step, hydrogen dissolved in thealloy melt influences the grain refinement effect. With increasing the cooling rate, the criticalhydrogen content increases too. It is expected that much hydrogen in the melt make the netinterfacial energy larger than or equal to zero, resulting in the shielding of the particles AlPduring solidification and that the critical gas content is closely related to the critical radius ofembryo bubbles.
文摘By making castings that pick up gas from moisture in red sand molds,the porosity generated at different cooling rates was discussed during solidification of hypereutectic Al-25%Si alloy without and with phosphorus additions. The effect of phosphorus addition on hydrogen content in the melt was also studied. It was observed that the phosphorus addition made hydrogen content in alloy melts present a “see-saw' tendency.In addition to primary silicon refinement,the phosphorus promoted gas porosity formed not only in slowly cooled sections, but also in rapidly cooled sections. There was a small difference in density of full dense sample between P-refined and unrefined castings, with a larger density associated with phosphorous addition. The change of the surface tension seemed more reasonable to explain the mechanism of porosity behavior.
基金supported by the Grant-in Aid for Scientific Research(23560898)the Support Program for Forming Strategic Research Infrastructure from the Ministry of Education,Science,Sports and Culture,Japan
文摘For the wider applications,it is necessary to improve the ductility as well as the strength and wear-resistance of hypereutectic AlSi-Cu alloys,which are typical light-weight wear-resistant materials.An increase in the amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys,but leads to the poor strength and ductility.It is known that dual phase steels composed of hetero-structure have succeeded in bringing contradictory mechanical properties of high strength and ductility concurrently.In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance,ultrasonic irradiation of the molten metal during the solidification,which is called sono-solidification,was carried out from its molten state to just above the eutectic temperature.The sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure,which are,hard primary silicon particles,soft non-equilibrium a-Al phase and the eutectic region.Rheo-casting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk specimen.After the rheo-casting with modified sonosolidified slurry held for 45 s at 570 oC,the quantitative optical microscope observation exhibits that the microstructure is composed of 18area%of hard primary silicon particles and 57area%of soft a-Al phase.In contrast,there exist only 5 area%of primary silicon particles and no a-Al phase in rheo-cast specimen with normally solidified slurry.Hence the tensile tests of T6 treated rheo-cast specimens with modified sono-solidified slurry exhibit improved strength and 5%of elongation,regardless of having more than 3 times higher amounts of primary silicon particles compared to that of rheo-cast specimen with normally solidified slurry.
文摘研究了A l-25%Si合金在半固态等温电磁搅拌条件下合金显微组织的变化行为.分别在580℃、600℃下等温搅拌0 m in、10 m in、20 m in和30 m in,实验结果显示:随着搅拌时间的增加,初生硅发生细化,尺寸明显变小且边角更加钝化,分布也更加均匀;当搅拌时间超过20 m in后,初生硅尺寸变化不大,分布趋于均匀.
