摘要
利用送粉式激光熔化3D打印工艺,研究了外加横向稳恒磁场对3D打印Al-12%Si合金构件凝固组织的影响。结果表明,在有/无横向稳恒磁场下,激光熔化单道薄壁试样的宏观凝固组织未发生明显改变,其主要以白亮带(以α-Al相为主)和灰暗区(以Al-Si共晶相为主)为基本单元叠加构成。而微观组织分析表明,无磁场时灰暗区内的初生α-Al相呈柱状枝晶形态,施加了0.35 T横向稳恒磁场后,试样灰暗区内的初生α-Al相全部转变为等轴枝晶形态,且枝晶臂发达。基于热电磁力及其Hartman无量纲数(用于表征稳恒磁场对金属熔体流动抑制作用的参数)估算分析表明,0.35 T稳恒磁场下,作用于初生α-Al枝晶上的热电磁力可达10~5N/m^3量级;Hartman数远大于10,表明激光熔化微小金属熔池中强烈的Marigoni以及热溶质对流一定程度上被抑制。分析认为,稳恒磁场下凝固组织灰暗区内α-Al相柱状枝晶向等轴枝晶的转变是固相中热电磁力(约10~5N/m^3)对枝晶的破碎作用导致,而等轴枝晶发达的枝晶臂则是横向稳恒磁场抑制熔体流动的结果。
Due to the great advantage in manufacturing component with complex structures, additive manufacturing（3D print）, essentially the rapid solidification of tiny metallic molten pool（hemisphere like with diameter ranging from dozens of microns to several millimeters） has become an important formation technique. Using powder laser melting, the effect of transverse static magnetic field on the solidified structure of additive manufactured Al-12%Si alloy was studied. The macrostructure was formed by white band（mainly primary α-Al phase） and dark grey area（mainly eutectic phase） and no obvious influencewas presented with or without static transverse magnetic field of 0.35 T. However, for the microstructure,the primary α-Al in dark grey area formed as columnar structure without magnetic field was found to transform to dendritic like with developed dendrite arms when under a static transverse magnetic field.The analysis on thermoelectricity and dimensionless Hartman parameter which used to characterize the restriction of static magnetic field on molten flows show that under a static transverse magnetic field of 0.35 T, the thermoelectric magnetic force can be as high as a magnitude of 10~5 N/m3, and Hartman values is far more than 10. The results indicate that the Marigoni and thermosolutal convection in laser melting pool was restricted. The transform from columnar to equiaxed dendrite of primary α-Al in dark grey area under static magnetic field was attributed to the fragmentation by thermoelectric magnetic force（105 N/m3） in solid phase. In addition, the formation of high order dendrite arms was supposed to be caused by the restriction of static magnetic field on the melt.
作者
帅三三
林鑫
肖武泉
余建波
王江
任忠鸣
SHUAI Sansan;LIN Xin;XIAO Wuquan;YU Jianbo;WANG Jiang;REN Zhongming(State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China;State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi＇an 710072, China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第6期918-926,共9页
Acta Metallurgica Sinica
基金
国家自然科学基金项目Nos.51690162和51604171
中国博士后基金项目Nos.2017T100291和2017M611530
西北工业大学凝固技术国家重点实验室开放课题项目Nos.SKLSP201706和SKLSP201602~~
关键词
增材制造
横向静磁场
Al-12%Si合金
CET转变
热电磁力
additive manufacturing
transverse static magnetic field
Al-12%Si alloy
columnar to equiaxed transition （CET）
thermoelectric magnetic force
