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Rapid solidification of undercooled Al-Cu-Si eutectic alloys
Ying Ruan,BingBo Wei
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-008-0540-x
Abstract: Under the conventional solidification condition, a liquid aluminium alloy can be hardly undercooled because of oxidation. In this work, rapid solidification of an undercooled liquid Al80.4Cu13.6Si6 ternary eutectic alloy was realized by the glass fluxing method combined with recycled superheating. The relationship between superheating and undercooling was investigated at a certain cooling rate of the alloy melt. The maximum undercooling is 147 K (0.18T E). The undercooled ternary eutectic is composed of α(Al) solid solution, (Si) semiconductor and θ(CuAl2) intermetallic compound. In the (Al+Si+θ) ternary eutectic, (Si) faceted phase grows independently, while (Al) and θ non-faceted phases grow cooperatively in the lamellar mode. When undercooling is small, only (Al) solid solution forms as the leading phase. Once undercooling exceeds 73 K, (Si) phase nucleates firstly and grows as the primary phase. The alloy microstructure consists of primary (Al) dendrite, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic at small undercooling, while at large undercooling primary (Si) block, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic coexist. As undercooling increases, the volume fraction of primary (Al) dendrite decreases and that of primary (Si) block increases.

CXDong,XYLuand BBWei,
,X.Y.Luand B.B.Wei

金属学报(英文版) , 1997,
Abstract: The Ag-Ge eutectic alloy system was intensively investigated with respect to its solidification characteristics at large undercoolings which were obtained by the B2O3 glass fluxing technique combined with argon protection. Grain size refinement was found in the Ag-15 wt% Ge hypoeuteciic alloy. With inereasing undercoolings the feather-like structure disappeared in the Ag-19wt% Ge eutectic alloy, and even silver slips showed up at sufficient undercoolings. Nevertheless, the fact that germanium had nucleated in preference to silver was indicated by a fine germanium line in the middle of the silver slips. The various morphologies of the germanium phase in the Ag-25 wt% Gehypereutectic alloy including the five-fold symmetry structure were explained by the joint action of high undercoolings (i.e. growth velocities) and density differences. The corpled zone of this alloy system was qualitatively estimated.

XING Liqian YANG Gencang ZHOU Yaohe GUO Zhenqi,

材料研究学报 , 1991,
Abstract: Bulk undercooled Ni-32.5 wt-%Sn melt was obtained by purifying themelt.The solidification process of the undercooled melt was studied.The formation of thevarious kinds of structures was analyzed.It is found that regular eutectic structure isformed if the

JF Li,GC Yang,YH Zhou,

金属学报(英文版) , 1998,
Abstract: The solidification behavior of bulk undercooled Ni50Cu50 alloy was systematically investigated. Double recalescences were discovered for the first time in a single phase Ni-Cd alloy, in which there is no solid phase transition at elevated temperature. When the alloy melt was undercoolcd below the solidus temperature, the effect of nonequilibrium solidification could make the solid with the norminal composition C0 of the alloy nucleate and grow till tempemture approached To (the temperuture at which the free enengies of solid and liquid with C0 are equal). Following it, the nucleation and growth of the solid with more high melting point component were required, so the secondary recalescence took place. The concentration distribution in crystals was also analysed.
Rapid solidification of acoustically levitated Al-Cu-Si eutectic alloy under laser irradiation
Na Yan,DeLu Geng,ZhenYu Hong,BingBo Wei
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4403-5
Abstract: Al-27%Cu-5.3%Si ternary eutectic alloy was melted using a YAG laser and then solidified while being acoustically levitated. A maximum undercooling to 195 K (0.24 T L) was achieved with a cooling rate of 76 K/s. The solidification microstructure was composed of (Al+θ+Si) ternary eutectics and (Al+θ) pseudobinary eutectics. During acoustic levitation, the (Al+θ+Si) ternary eutectics are refined and the (Al+θ) pseudobinary eutectics have morphological diversity. On the surface of the alloys, surface oscillations and acoustic streaming promote the nucleation of the three eutectic phases and expedite the cooling process. This results in the refinement of the ternary eutectic microstructure. During experiments, the reflector decreases with increasing alloy temperature, and the levitation distance always exceeds the resonant distance. Because of the acoustic radiation pressure, the melted alloy was flattened, and deformation increases with increasing sound pressure. The maximum aspect ratio achieved was 6.64, corresponding to a sound pressure of 1.8×104 Pa.
Solidification Structure Formation of Undercooled Single Phase Alloys
Jinfu LI,Yaohe ZHOU,Wanqi JIE,Gencang YANG,
Jinfu LU and Yaohe ZHOUSchool of Materials Science and Engineering
,Shanghai Jiao Tong University,Shanghai,ChinaWanqi JIE and Gencang YANGState Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi''''an,Chin

材料科学技术学报 , 2002,
Abstract: Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied. The progress, especially during the last decade, is reviewed so as to give a comprehensive knowledge for it, in which the emphases are laid on the structure evolution mechanism and the potential application. Lastly, the future interesting subjects are presented.
GUO Jingjie JIA Jun LI Qingchun LI Bangsheng Harbin Institute of Technology,Harbin,China,
GUO Jingjie JIA Jun LI Qingchun LI Bangsheng Harbin Institute of Technology

金属学报(英文版) , 1992,
Abstract: The eutectic growth of cast iron during rapid solidification has been studied with laser remelt- ing and deep etching technology.A new mode of mushroom eutectic growth was observed oth- er than the usual honeycomb and lamellar ones.The mushroom eutectic growth may finally form the lamellar dendritic structure.
Evolution of eutectic spacing during unidirectional solidification of Al-Ni alloys
Araujo, Igor Jefferson Cabral;Silva, Bismarck Luiz da;Spinelli, José Eduardo;Garcia, Amauri;
Materials Research , 2011, DOI: 10.1590/S1516-14392011005000034
Abstract: hypoeutectic al-ni alloys show a ductile phase α distributed with a β phase al3ni fragile where β serves as reinforcement of the structure of the material. the eutectic composition alloys obey the relationship: λ2.v = c, where λ is the eutectic spacing, v is a tip growth rate and c is a constant. the aim of this study is to establish correlations between λ and v for hypoeutectic al-1%, 3% and 5% ni alloys. unsteady-state upward directional solidification experiments were performed, as well as metallography, dissolution of the aluminum matrix and scanning electron microscopy (sem). the interphase spacing of the three al-ni alloys decreased with increasing tip growth rate, with a predominance of a rod-like morphology on intermetallic. it was observed that parameters such as tip growth rate, cooling rate and temperature gradient decreases as the solidification front advances. it was further observed that a single experimental law λ = 1.2 v-0, 5 illustrates the evolution of the interphase spacing for any examined alloy.
Formation mechanism of anomalous eutectics in highly undercooled Ag--39.9 at%Cu alloy

Zhao Su,Li Jin-Fu,Liu Li,Zhou Yao-He,

中国物理 B , 2009,
Abstract: This paper investigates the solidification behaviour of the Ag--Cu eutectic alloy melt undercooled up to 100K. It is revealed that lamellar eutectics grow in a dendritic form in the Ag--Cu eutectic melt with undercooling equal to or greater than 76K. As undercooling increases, the remelted fraction of the primary eutectics during recalescence rises. The severe remelting and the subsequent ripening of the primary eutectic dendrites lead to the formation of anomalous eutectics.
Phase-selection and metastable phase formation in highly undercooled eutectic Ni78.6Si21.4 alloys
LU Yiping,YANG Gencang,YANG Changlin,WANG Haipeng,ZHOU Yaohe,
LU Yiping
,YANG Gencang,YANG Changlin,WANG Haipeng,ZHOU Yaohe

自然科学进展 , 2006,
Abstract: A large undercooling (250 K) was achieved in eutectic Ni78.6Si21.4 melt by the combination of molten-glass denucleation and cyclic superheating. The metastable phase formation process in the bulk undercooled eutectic Ni78.6Si21.4 melts was investigated. With the increase of undercooling, different metastable phases form in eutectic Ni78.6Si21.4 melts and part of these metastable phases can be kept at room temperature through slow post-solidification. Under large undercooling, the metastable phases β2-Ni3Si, Ni31Si12 and Ni3Si2 were identified. Especially, the Ni3Si2 phase was obtained in eutectic Ni78.6Si21.4 alloy for the first time. Based on the principle of free energy minimum and transient nucleation theory, the solidification behavior of melts was analyzed with regard to the metastable phase formation when the melts were in highly undercooled state.
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