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液相流动对柱晶一次间距的影响

刘山 , 鲁德洋 , 黄韬 , 周尧和

金属学报

利用带有对流驱动系统的定向凝固装置,研究了液相稳定流动时透明合金SCN-2wt-％Ace定向凝固的动态过程.结果表明:流动显著改变定向凝固柱状晶的一次间距枝晶的间距增大,主要是流动与枝端浓度场耦合作用的结果;胞晶的间距变小,主要是侧向分枝转向生长的结果

关键词: 液相强迫流动 , directional solidification , dendrite spacing , cell spacing

EFFECT OF LIQUID FLOW ON PRIMARY ARM SPACING OF CONSTRAINED COLUMNAR CRYSTALS

LIU Shan LU Deyang HUANG Tao ZHOU Yaohe National Lab of Solidification Processing , Northwestern Polytechnical University , Xi'an , China LIU Shan , lecturer , National Laboratory of Solidification Processing , Northwestern Polytechnical University , Xi'an 710072 , China

金属学报(英文版)

An experimental apparatus,which has a convection generator and an aid-heater,is developed for the study of the effect of stable laminar liquid flow on the directional solidification process by the use of transparent alloy SCN-2wt-% Ace.The flow is perpendicular to primary arms. By in-situ observation and photographing at different specific moments,it has been found that such a flow can cause a great change in primary spacings of constrained columnar crystals:for cells,the spacings become smaller;but for dendrites,they become larger.The former is mainly due to the tilted growth of upstreamside branches,while the latter is mainly due to the coup- ling effect of liquid flow with solutal field around dendrite tips.The faster the liquid flows,the further smaller the cell spacing and the further larger the dendrite spacing.

关键词: forced liquid flow , null , null , null

EXPERIMENTAL RESEARCH ON DIRECTIONAL SOLIDIFICATION OF Al-4.5wt%Cu ALLOY BY ACRT METHOD

JIE Wanqi(State Key Laboratory of Solidification Processing , Northwestern Polytechnical University , Xi'an 710072 , China) Manuscript received 25 May 1995

金属学报(英文版)

Accelerated crucible rotation technique(ACRT) has been used for the directional solidification of Al-4.5wt% Cu binary alloy.By rotating the crucible at varying rate and direction,forced liquid flows are aroused These flows include Ekman flow,Couette flow and Spiral Shear flow.Especially,Ekman flow acts directly at the L/S interface,changes diffusion and heat exchange conditions and has strong influences on the morphology of L/S interface.Experimental results show that,compared with normal Bridgman specimens,the solidification region is much narrower and the cell spacing is much smaller in ACRT specimens.These influences become much stronger when the accelerating rate is increased.

关键词: :accelerated crucible rotation technique(ACRT) , null , null , null , null

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