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
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
A novel crystal nucleus-based cement-hardening accelerator was evaluated using various mortar and segment concrete experiments.The mechanism of hardening acceleration was investigated via hydration temperature variati...A novel crystal nucleus-based cement-hardening accelerator was evaluated using various mortar and segment concrete experiments.The mechanism of hardening acceleration was investigated via hydration temperature variation analysis,hydration degree analysis,X-ray diffraction(XRD)and scanning electron microscopy(SEM).In the presence of accelerator,the fluidity loss of mortar was increased after 30 minuites,and a coagulation was also observed.Moreover,based on the image of SEM,the formation of C-S-H gels was enhanced in the early hydration.As a result,the hardening accelerator could significantly boost the early strength of concrete,especially within one day of pouring,and shorten steam curing time to meet the demolding strength.展开更多
Molecular dynamics simulation method was used to study the influence of NO2^- on both the structure and properties of the binary nitrate salts(60 wt.% NaNO3 + 40 wt.% KNO3). The density and viscosity of the mixtures w...Molecular dynamics simulation method was used to study the influence of NO2^- on both the structure and properties of the binary nitrate salts(60 wt.% NaNO3 + 40 wt.% KNO3). The density and viscosity of the mixtures were experimentally measured and the simulation results met well with the experimental ones. The simulation results showed that, with the addition of NO2^-, the ionic clusters tended to loose and the mobilities of all the ions tended to increase. The density, viscosity, and heat capacity decreased while the thermal conductivity increased with the increase of NO2^- concentration. The correlation between the microscopic structure and physical properties of the mixtures were discussed and revealed.展开更多
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.
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Funded by Star Program(No.1804QB1403200)from Science and Technology Commission of Shanghai Municipality。
文摘A novel crystal nucleus-based cement-hardening accelerator was evaluated using various mortar and segment concrete experiments.The mechanism of hardening acceleration was investigated via hydration temperature variation analysis,hydration degree analysis,X-ray diffraction(XRD)and scanning electron microscopy(SEM).In the presence of accelerator,the fluidity loss of mortar was increased after 30 minuites,and a coagulation was also observed.Moreover,based on the image of SEM,the formation of C-S-H gels was enhanced in the early hydration.As a result,the hardening accelerator could significantly boost the early strength of concrete,especially within one day of pouring,and shorten steam curing time to meet the demolding strength.
基金This project is supported by Grant 51774144 and U1407126 from the National Natural Science Foundation of ChinaGrant 2018YFC1903803 from the National Key R&D Program of ChinaThe following local government funding also supported this project:Grant 2017-ZJ-727 and 2018-ZJ-738 from Applied basic research of Qinghai Province,Grant 2015-GX-Q19A from Capacity Building of Qinghai Engineering Research Center for Integrated Utilization of Salt Lake and the Fundamental Research Funds for the Central Universities。
文摘Molecular dynamics simulation method was used to study the influence of NO2^- on both the structure and properties of the binary nitrate salts(60 wt.% NaNO3 + 40 wt.% KNO3). The density and viscosity of the mixtures were experimentally measured and the simulation results met well with the experimental ones. The simulation results showed that, with the addition of NO2^-, the ionic clusters tended to loose and the mobilities of all the ions tended to increase. The density, viscosity, and heat capacity decreased while the thermal conductivity increased with the increase of NO2^- concentration. The correlation between the microscopic structure and physical properties of the mixtures were discussed and revealed.
