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Calculation Models of Mass Action Concentrations for Metallic Melts Involving monotectic

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Journal of University of Science and Technology Beijing 2001年第4期8卷 248-253页

作者： Jian Zhang Metallurgy School, University of Science and Technology Beijing, Beijing 100083, China Metallurgy School University of Science and Technology Beijing Beijing 100083 China

Based on the phase diagrams, measured activities as well asDeltaG(m) and DeltaG(xs), calculating models of mass action concentrations for metallic melts involving monotectic have been formulated. The calculated results agree with practice on the whole, showing that the models deduced generally can reflect the structural characteristics of these melts. The metastable compounds formed in the melts are of the types A(2)B(3), AB(2), A(2)B(3) or AB and A(2)B(3)+AB etc..

关键词： metallic melts monotectic activity mass action concentration

Microstructure Evolution of Cu-Pb monotectic Alloys Processed in Drop Tube

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Journal of Materials Science & Technology 2002年第1期18卷 73-76页

作者： Cao, CD Wei, BB Northwestern Polytech Univ Dept Appl Phys Xian 710072 Peoples R China

The rapid solidification of Cu-Pb monotectic alloys has been accomplished during free fall in a 3 m drop tube. Both macrosegregated and uniformly dispersed structures are observed in droplets of Cu-40 wt pct Pb alloy, whereas droplets of Cu-64 wt pct Pb alloy exhibit only macrosegregation morphologies. The microstructure is strongly dependent on the droplet size. The higher undercooling tends to facilitate the liquid phase separation and results in more extensive macrosegregation in smaller droplets. There exists a pronounced tendency for the Pb-rich liquid to occupy the surface of the droplets of both compositions, resulting from the quite lower surface tension of the Pb-rich phase and causing a Pb-rich layer at the surface of the solidified droplet. The nucleation of monotectic cells in the Cu-40 wt pct droplets with dispersed structures preferentially occurs at the droplet surface. The single nucleation event takes place more frequently as the droplet size is reduced.

关键词： Rapid solidification Undercooling Immiscibility Containerless processing Low-gravity monotectic

Rapid monotectic solidification under free fall condition

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Science China(Technological Sciences) 2004年第4期47卷 409-420页

作者： LIU Xiangrong LU Xiaoyu WEI Bingbo Laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China Laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China Laboratory of Materials Science in Space Department of Applied Physics Northwestern Polytechnical University Xi'an 710072 China

Fe-48.8% Sn monotectic, Fe-40% Sn hypomonotectic and Fe-58% Sn hypermonotectic alloys have been rapidly solidified during free fall processing in drop tube. For droplets of 100—1000 mm, the maximum undercooling for Fe-48.8% Sn, Fe- 40% Sn and Fe-58% Sn alloys is 270, 282 and 288 K respectively. For Fe-48.8% Sn monotectic alloy, a homogeneously dispersed microstructure can be obtained when the droplet diameter is small, and the Marangoni migration velocity Vm is 37 times as fast as Stokes velocity Vs when the dispersion sphere radius is 6 mm and undercooling is 30 K. For Fe-40% Sn hypomonotectic alloy, the microstructure undergoes a transition from columnar a-Fe dendrites distributed in Sn-rich matrix to a-Fe particles. The growth velocity of a-Fe dendrite changes from 0.45 to 4.65 m/s when the droplet diameter varies from 1000 to 100 mm. For Fe-58.8% Sn hypermonotectic alloy, the grain size of primary a-Fe dendrites decreases remarkably when undercooling increases.

关键词： monotectic solidification, phase separation, undercooling, containerless processing.

Some Physicochemical and Thermal Studies on Organic Analog of a Nonmetal-Nonmetal monotectic Alloy;2-Cyanoacetamide–4-chloronitrobenzene System

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American Journal of Analytical Chemistry 2011年第8期2卷 953-961页

作者： Manjeet Singh Rama Nand Rai Uma Shankar Rai 不详

The phase equilibrium data on organic analog of the nonmetal-nonmetal system, involving 2-cyanoacetamide (CA)―4-chloronitrobenzene (CNB), show the formation of a monotectic (0.10 mole fraction of CNB) and a eutectic (0.98 mole fraction of CNB) with a large miscibility gap starting from 0.10 mole fraction of CNB of monotectic (M) and ending at 0.92 mole fraction of CNB of monotectic horizontal (Mh);the upper consolute temperature Tc being 63?C above the monotectic horizontal at 118?C and eutectic temperature is at 85?C. The values of enthalpy of fusion of the pure components, the eutectic and the monotectic were determined by the differential scanning calorimetry (Mettler DSC-4000 system). Using these data, the size of the critical radius, interfacial energy, excess thermodynamic functions, entropy of fusion, and enthalpy of mixing were calcu-lated. The solid-liquid interfacial energy data confirm the applicability of the Cahn wetting condition. While growth data obey the Hillig-Turnbull equation, the microstructural investigations give typical characteristic features of the eutectic and the monotectic of the system.

关键词： Phase Diagram Thermal Properties Eutectic Composite monotectic Alloys Interfacial Energy Microstructure Solvent Free Synthesis

Specific heat and related thermophysical properties of liquid Fe-Cu-Mo alloy

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 397-406页

作者： WANG HaiPeng LUO BingChi CHANG Jian WEI BingBo Department of Applied Physics Northwestern Polytechnical UniversityXi’an 710072China

The specific heat and related thermophysical properties of liquid Fe77.5Cu13Mo9.5 monotectic alloy were investigated by an electromagnetic levitation drop calo-rimeter over a wide temperature range from 1482 to 1818 K.A maximum under-cooling of 221 K(0.13 Tm)was achieved and the specific heat was determined as 44.71 J·mol1·*** excess specific heat,enthalpy change,entropy change and Gibbs free energy difference of this alloy were calculated on the basis of experimental *** was found that the calculated results by traditional esti-mating methods can only describe the solidification process under low under-cooling *** the experimental results can reflect the reality under high undercooling ***,the thermal diffusivity,thermal conductivity,and sound speed were derived from the present experimental ***,the solidified microstructural morphology was examined,which consists of(Fe)and(Cu)*** calculated interface energy was applied to exploring the correlation between competitive nucleation and solidification microstructure within monotectic alloy.

关键词： high undercooling specific heat monotectic alloy thermophysical property rapid solidification