合金凝固枝晶粗化的研究進(jìn)展

合金凝固枝晶粗化的研究進(jìn)展Progresses in Dendrite Coarsening During Solidifiction of Alloys

枝晶是一種最常見(jiàn)的金屬凝固顯微組織。在大多數(shù)中、低速的凝固過(guò)程中，枝晶組織發(fā)生粗化是一種不可避免的現(xiàn)象，對(duì)最終的凝固組織和產(chǎn)品性能產(chǎn)生重要影響。本文首先簡(jiǎn)要評(píng)述半個(gè)多世紀(jì)以來(lái)關(guān)于連續(xù)冷卻和等溫凝固過(guò)程中的枝晶粗化在理論研究、實(shí)驗(yàn)研究和數(shù)值模擬3方面的研究進(jìn)展。隨后，介紹作者課題組最近提出的一個(gè)包含凝固和熔化機(jī)制的元胞自動(dòng)機(jī)(cellular automaton, CA)模型。采用該CA模型對(duì)SCN-ACE合金在固/液兩相區(qū)等溫過(guò)程中的枝晶粗化現(xiàn)象進(jìn)行模擬研究，對(duì)枝晶粗化過(guò)程中的凝固/熔化、界面幾何形狀和溶質(zhì)擴(kuò)散之間的復(fù)雜相互作用關(guān)系進(jìn)行分析。

Dendrites are the most frequently observed solidification microstructure of metallic alloys. In most solidification processes at low and moderate cooling rates, dendrite coarsening in mushy zones has been recognized as an unavoidable phenomenon that significantly influences microstructures and thereby the properties of the final products. The behavior of dendrite coarsening has received persistent scientific interest owing to its importance for both academic value and practical application. During the last five decades, extensive efforts have been made through theoretical analyses, experimental techniques and numerical simulations for fundamentally understanding the mechanisms of dendrite coarsening during solidification under continuously cooling or isothermal conditions. This paper first gives a brief overview of the progress in the studies of dendrite coarsening. Then, a CA model recently proposed by the authors is presented, which involves the mechanisms of both solidification and melting. The model is applied to simulate the microstructural evolution of columnar dendrites of SCN–ACE alloys during isothermal holding in a mushy zone. The CA simulations reproduce the typical dendrite coarsening features as observed in experiments reported in the literature. The role of melting for dendrite coarsening is quantified by comparing the simulation results using the new CA model and a previous CA model that does not include the melting effect. The mechanisms of dendrite coarsening are investigated in detail by comparing the local equilibrium and actual liquid compositions at solid/liquid interfaces. The CA simulations render visualizing how local solidification and melting stimulate each other through the complicated interactions between phase transformation, interface shape variation, and solute diffusion.

全文下載：https://pan.baidu.com/s/17g-2R5X5Js5Vkm1mtQchOQ?

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