Semi-solid ingots of an A1SiTMg alloy were obtained using the method of near liquidus casting. Their microstructures exhibit the characteristics of free, equiaxed, and non-dendrite, which are required for semi-solid f...Semi-solid ingots of an A1SiTMg alloy were obtained using the method of near liquidus casting. Their microstructures exhibit the characteristics of free, equiaxed, and non-dendrite, which are required for semi-solid forming. The influences of casting temperature, heat preservation time, and cooling rate on the microstructure were also investigated. The results show that in the temperature region near liquidus the grain size becomes small with a decrease in casting temperature. Prolonging the heat preservation time makes grain crassitude at the same temperature. And increasing the cooling rate makes grain fine. The microstructure of the alloy cast with iron mould is freer than that with graphite mould.展开更多
The microstructures of ZL201 alloy slurry prepared by near-liquidus electromagnetic casting （NLEMC）, electromagnetic casting（EMC）, and near-liquidus casting（NLC） were investigated by means of electron microscopy...The microstructures of ZL201 alloy slurry prepared by near-liquidus electromagnetic casting （NLEMC）, electromagnetic casting（EMC）, and near-liquidus casting（NLC） were investigated by means of electron microscopy and image analysis. Mechanical properties of as-cast alloys were determined. The results show that the NLEMC induces a fine, uniform, and equiaxed grain structure with a mean equal-area-circle grain diameter of 32.8μm. The as-cast aUoy has a hardness of HV122.8 and a tensite strength of 368MPa. Both of them are betterthan those of the alloys prepared by EMC and by NLC. The mechanism of grain refinement in the NLEMC alloy slurry was discussed.展开更多
The semi-solid billet of 6061 aluminum alloy was prepared by the near-liquidus semi-continuous casting（LSC） with rosette or near-spheroide grains.The pre-deformation processing was applied before partial remelting t...The semi-solid billet of 6061 aluminum alloy was prepared by the near-liquidus semi-continuous casting（LSC） with rosette or near-spheroide grains.The pre-deformation processing was applied before partial remelting to further improve the microstructure and properties of the semi-solid alloy.The effects of different processing parameters,such as holding temperature and holding time,on the semisolid microstructures during partial remelting have been investigated.It was found that the optimal partial remelting parameters should be 630℃ and 10-15 min for 6061 alloy cold rolled with 60% reduction in height of pre-deformation.The coarsening rates were anasysed by Lifshitz-Slyozov-Wagner（LSW） theory.The pre-deformed 6061 alloy exhibits lower coarsening rate constants than that of the as-cast one,and also lower than other alloys processed by different method found in previous literature.It is because the coarsening rate is associated with the initial microstructure and composition of the alloy.The secondary phases in the alloy inhibit the migration of the liquid film grain boundaries.The microstructure obtained by using the combination of near-liquidus semicontinuous casting and pre-deformation treatment is better than that without pre-deformation processing,which demonstrates that the used method is promising for fabricating high quality semi-solid alloys.展开更多
An electromagnetic stirring process near liquidus temperature was designed and demonstrated experimentally to produce semi-solid slurry of AZ91 magnesium alloy,in order to avoid not only contamination from mechanical ...An electromagnetic stirring process near liquidus temperature was designed and demonstrated experimentally to produce semi-solid slurry of AZ91 magnesium alloy,in order to avoid not only contamination from mechanical stirring but also the inflammation of Mg alloy melt at elevated temperature. AZ91 alloy feedstock was isothermally heat treated at 600-610 for 20 min,and then stirred by electromagnetic field. Globular primary particle characteristic was observed optically in the castings. Mechanical properties were also studied.展开更多
The semi-solid forward-extruding feasibility of reheated ZL116 alloy cast by the near-liquidus semi-continuous casting process was studied by analyzing the microstructures and properties of forward-extruded bars. The ...The semi-solid forward-extruding feasibility of reheated ZL116 alloy cast by the near-liquidus semi-continuous casting process was studied by analyzing the microstructures and properties of forward-extruded bars. The results show that the microstructure of the ZL116 alloy billets cast by near-liquidus semi-continuous casting is mainly made up of homogeneous, fine global-or rosette-shaped grains. The microstructure of the billets, reheated and held at 575℃, contains stable and net-spherical grains which are suitable for semi-solid thixoforming. The semi-solid forward-extruded bars of the ZL116 alloy billet are facially smooth, microstructurally fine and homogeneous. Therefore the feasibility of semi-solid forward-extrusion of ZL116 alloy is thus excellent.展开更多
基金the National Natural Science Foundation of China (No. 50374031)the Aviation Science Foundation of Liaoning Province (No. 20054003)+1 种基金the Education Committee of Liaoning Province (No. 05L415)the Research Foundation of the Experimental Center of SYNU.]
文摘Semi-solid ingots of an A1SiTMg alloy were obtained using the method of near liquidus casting. Their microstructures exhibit the characteristics of free, equiaxed, and non-dendrite, which are required for semi-solid forming. The influences of casting temperature, heat preservation time, and cooling rate on the microstructure were also investigated. The results show that in the temperature region near liquidus the grain size becomes small with a decrease in casting temperature. Prolonging the heat preservation time makes grain crassitude at the same temperature. And increasing the cooling rate makes grain fine. The microstructure of the alloy cast with iron mould is freer than that with graphite mould.
基金This work was supported by the National Natural Science Foundation of China(No.50374031)National High Technical Reasearch and Development Programme of China(No.2003AA305090)Liaoning Provincial Natural Science Foundation of China(No.20031011).
文摘The microstructures of ZL201 alloy slurry prepared by near-liquidus electromagnetic casting （NLEMC）, electromagnetic casting（EMC）, and near-liquidus casting（NLC） were investigated by means of electron microscopy and image analysis. Mechanical properties of as-cast alloys were determined. The results show that the NLEMC induces a fine, uniform, and equiaxed grain structure with a mean equal-area-circle grain diameter of 32.8μm. The as-cast aUoy has a hardness of HV122.8 and a tensite strength of 368MPa. Both of them are betterthan those of the alloys prepared by EMC and by NLC. The mechanism of grain refinement in the NLEMC alloy slurry was discussed.
基金financially supported by the National Natural Science Foundation of China (Grant No.50674032)
文摘The semi-solid billet of 6061 aluminum alloy was prepared by the near-liquidus semi-continuous casting（LSC） with rosette or near-spheroide grains.The pre-deformation processing was applied before partial remelting to further improve the microstructure and properties of the semi-solid alloy.The effects of different processing parameters,such as holding temperature and holding time,on the semisolid microstructures during partial remelting have been investigated.It was found that the optimal partial remelting parameters should be 630℃ and 10-15 min for 6061 alloy cold rolled with 60% reduction in height of pre-deformation.The coarsening rates were anasysed by Lifshitz-Slyozov-Wagner（LSW） theory.The pre-deformed 6061 alloy exhibits lower coarsening rate constants than that of the as-cast one,and also lower than other alloys processed by different method found in previous literature.It is because the coarsening rate is associated with the initial microstructure and composition of the alloy.The secondary phases in the alloy inhibit the migration of the liquid film grain boundaries.The microstructure obtained by using the combination of near-liquidus semicontinuous casting and pre-deformation treatment is better than that without pre-deformation processing,which demonstrates that the used method is promising for fabricating high quality semi-solid alloys.
基金The project was supported by the National Natural Science Foundation of China (No.50374014).
文摘An electromagnetic stirring process near liquidus temperature was designed and demonstrated experimentally to produce semi-solid slurry of AZ91 magnesium alloy,in order to avoid not only contamination from mechanical stirring but also the inflammation of Mg alloy melt at elevated temperature. AZ91 alloy feedstock was isothermally heat treated at 600-610 for 20 min,and then stirred by electromagnetic field. Globular primary particle characteristic was observed optically in the castings. Mechanical properties were also studied.
基金the National Key Scientific and Technical Research Program of China (106058)National Doctoral Program Foundation of China (20050145007)National Natural Science Foundation (50674032).
文摘The semi-solid forward-extruding feasibility of reheated ZL116 alloy cast by the near-liquidus semi-continuous casting process was studied by analyzing the microstructures and properties of forward-extruded bars. The results show that the microstructure of the ZL116 alloy billets cast by near-liquidus semi-continuous casting is mainly made up of homogeneous, fine global-or rosette-shaped grains. The microstructure of the billets, reheated and held at 575℃, contains stable and net-spherical grains which are suitable for semi-solid thixoforming. The semi-solid forward-extruded bars of the ZL116 alloy billet are facially smooth, microstructurally fine and homogeneous. Therefore the feasibility of semi-solid forward-extrusion of ZL116 alloy is thus excellent.
