垂直向上凝固Al-Cu铸件中微观孔洞形成的数值模拟  

MODELING OF MICROPOROSITY FORMATION IN UPWARD VERTICALLY SOLIDIFIED Al-Cu CASTING

作　　者：赵海东[1] 吴朝忠[1] 李元元[1] 大中逸雄[2] 

机构地区：[1]华南理工大学机械工程学院,广州510640 [2]大阪大学智能工专系,大阪5650871

出　　处：《金属学报》2008年第11期1340-1347,共8页Acta Metallurgica Sinica

基　　金：教育部科学技术重点研究项目105138;教育部留学回国人员基金项目2004527;日本产学官联合革新的铸造模拟技术项目11305054资助~~

摘　　要：基于枝晶间流动的Darcy定律,考虑了凝固过程氢的宏观扩散与传输,建立了耦合氢宏观偏析的铝合金铸件微观孔洞形成的数学模型,并进行了实时熔炼的Al-4.5%Cu(质量分数)铸件的垂直向上凝固实验,铸件微观组织和孔洞的分析结果表明:铸件沿着高度方向包括了柱状晶、柱状晶向等轴晶转变(CET)和等轴晶3个区域;柱状晶区域内微观孔洞体积分数存在递减的分布规律,且邻近底部冷模的试样微观孔洞体积分数最大.采用所建立的模型对实验铸件微观孔洞形成进行了模拟,模拟结果与实验结果吻合较好;而当忽略氢宏观偏析时,模拟结果与实验结果存在较大误差.研究表明,氢的宏观偏析对微观孔洞的形核与分布具有重要影响.Based on Darcy＇s law for interdendritic flow,a mathematical model for hydrogen porosity formation in Al castings was developed,in which the hydrogen macrosegregation including hydrogen diffusion and transport in macroscopic scale was considered.An upward unidirectional solidification experiment of Al-4.5%Cu（mass fraction）casting in situ melted was carried out.The microstructure analysis showed that the casting consists of columnar crystal,CET（columnar-toequiaxed transition）and equiaxed crystal regions along upward direction.It was found that there exists a gradually decreasing distribution of porosity in the columnar region,and the porosity in casting part near the bottom chill is higher.The proposed model was applied to the experimental casting,and the simulation results are in well agreement with the experiment results only when the hydrogen macrosegregation was considered.The hydrogen macrosegregation has significant influence on the predicted porosities,especially their nucleation and distribution.

关 键 词：微观孔洞 数值模拟 Al-Cu铸件 氢宏观偏析 

分 类 号：TG292[金属学及工艺—铸造] TG146.21[一般工业技术—材料科学与工程]