摘要
枝晶是一种最常见的金属凝固显微组织。在大多数中低速的凝固过程中,枝晶组织发生粗化是一种不可避免的现象,对最终的凝固组织和产品性能产生重要影响。本文首先简要评述半个多世纪以来关于连续冷却和等温凝固过程中的枝晶粗化在理论研究、实验研究和数值模拟3方面的研究进展。随后,介绍作者课题组最近提出的一个包含凝固和熔化机制的元胞自动机(cellular automaton,CA)模型。采用该CA模型对SCNACE合金在固/液两相区等温过程中的枝晶粗化现象进行模拟研究,并对枝晶粗化过程中的凝固/熔化、界面几何形状和溶质扩散之间的复杂相互作用关系进行分析。
Dendrites are the most frequently observed solidification microstructures 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 interests owing to its importance in 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 cellular automaton（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 SCNACE alloys during isothermal holding in a mushy zone. The CA simulations reproduce the typical dendritecoarsening features as observed in experiments. 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.
作者
朱鸣芳
邢丽科
方辉
张庆宇
汤倩玉
潘诗琰
ZHU Mingfang;XING Like;FANG Hui;ZHANG Qingyu;TANG Qianyu;PAN Shiyan(Jiangsu Key Laboratory for Advanced Metallic Materials, Southeast University, Nanjing 211189, China;School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第5期789-800,共12页
Acta Metallurgica Sinica
基金
国家自然科学基金项目Nos.51371051和51501091
中央高校基本科研业务费专项资金项目No.2242016K40008
江苏省先进金属材料高技术研究重点实验室创新科研项目No.BM2007204
东南大学优秀博士论文培育基金项目No.YBJJ1627~~
关键词
合金凝固
显微组织
枝晶粗化
元胞自动机法
alloy solidification
microstructure
dendrite coarsening
cellular automaton method
