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金属学报  2014, Vol. 50 Issue (8): 921-929    DOI: 10.11900/0412.1961.2014.00013
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单室Gasar工艺中抽拉速率对藕状多孔Cu气孔形貌的影响*
卓伟佳1, 刘源1,2(), 李言祥1,2
1 清华大学材料学院, 北京 100084
2 清华大学机械工程系先进成形制造教育部重点实验室, 北京 100084
EFFECT OF WITHDRAWING RATE ON PORE MORPHOLOGY OF LOTUS-TYPE POROUS COPPER PRODUCED BY SINGLE-MOLD GASAR TECHNIQUE
ZHUO Weijia1, LIU Yuan1,2(), LI Yanxiang1,2
1 School of Materials Science and Engineering, Tsinghua University, Beijing 100084
2 Key Laboratory for Advanced Materials Processing Technology (Ministry of Education), Department of
Mechanical Engineering, Tsinghua University, Beijing 100084
引用本文:

卓伟佳, 刘源, 李言祥. 单室Gasar工艺中抽拉速率对藕状多孔Cu气孔形貌的影响*[J]. 金属学报, 2014, 50(8): 921-929.
Weijia ZHUO, Yuan LIU, Yanxiang LI. EFFECT OF WITHDRAWING RATE ON PORE MORPHOLOGY OF LOTUS-TYPE POROUS COPPER PRODUCED BY SINGLE-MOLD GASAR TECHNIQUE[J]. Acta Metall Sin, 2014, 50(8): 921-929.

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摘要: 

采用单室Gasar工艺, 通过实验研究和Procast凝固模拟相结合, 研究了坩埚抽拉速率对凝固界面形貌、铸锭平均凝固速率、藕状多孔Cu气孔形貌、气孔生长方向以及相应多孔结构参数的影响规律. 研究表明, 随着抽拉速率的升高, 凝固界面从凸界面向平界面再向凹界面演化. 当凝固界面为凸界面和凹界面时, 气孔生长方向都会偏离铸锭抽拉方向. 而只有在合适的抽拉速率条件下使凝固界面以平界面方式推进, 才能获得气孔完全平直生长的优质藕状多孔Cu. 实验和模拟结果显示, 在本实验条件下, 当抽拉速率为1 mm/s时, 铸锭凝固界面基本以平界面方式推进; 藕状多孔Cu铸锭的气孔率不受抽拉速率的影响, 但随着抽拉速率的增大, 平均孔径和通孔率会逐渐降低.

关键词 藕状多孔Cu单室Gasar工艺抽拉速率气孔形貌    
Abstract

A single mold Gasar process was developed to fabricate lotus-type porous copper with long and straight pores. The effects of withdrawing rate on the solidification front shape, pore morphology and average solidification rate of porous copper ingots were investigated through experimental study and Procast simulation. The results show that the solidification front shape evolves from convex to planar, then to concave with increasing withdrawing rate. In this work, 1.0 mm/s is an appropriate rate for planar solidification front. In this case, all of the gas pores grow along the axial direction (parallel to the withdrawing direction) and the pores′ straightness is the best. The average porosities of copper ingots are constant and independent of the withdrawing rate. But the average pore diameter and penetration ratio of gas pores decreased with increasing withdrawing rate.

Key wordslotus-type porous copper    single mold Gasar process    withdrawing rate    pore morphology
收稿日期: 2014-01-06     
ZTFLH:  TG249.6  
基金资助:* 国家自然科学基金项目51271096和新世纪优秀人才计划项目NCET-12-0310资助
作者简介: null

卓伟佳, 1988年生, 男, 硕士

图1  单室Gasar工艺示意图
图2  不同抽拉速率下制备的藕状多孔Cu的纵截面图
图3  抽拉速率对气孔生长方向影响示意图
图4  抽拉速率为5 mm/s的藕状多孔Cu不同高度上横截面的气孔形貌
图5  致密凝固层及边缘椭球形大气泡形成原因示意图
图6  抽拉速率对藕状多孔Cu铸锭平均气孔率的影响
图7  抽拉速率对藕状多孔Cu平均孔径的影响
图8  抽拉速率对藕状多孔Cu通孔率的影响(沿孔长方向试样高度20 mm)
图9  Gasar凝固中气孔的生长中断和二次形核示意图
图10  单室Gasar炉内气氛温度分布、温度场物理模型和相应边界条件
Parameter Value Unit
Heat conductivity of graphite crucible, lgraphite 131.06-0.0425T W/(m·K)
Density of graphite crucible, rgraphite 2200 kg/m3
Specific heat of graphite crucible, Cpgraphite 0.71 kJ/(kg·K)
Emissivity of heater, eheater 0.98[23]
Emissivity of graphite crucible, ecrucible 0.98[23]
Emissivity of copper and chiller, ecopper 0.78[23]
Convection heat transfer coefficient, hcrucible/gas 200* W/(m2·K)
Convection heat transfer coefficient, hmelt/gas 200* W/(m2·K)
Convection heat transfer coefficient, hchiller/gas 200* W/(m2·K)
Interfacial heat transfer coefficient, hcrucible/solid copper 3000[24] W/(m2·K)
Interfacial heat transfer coefficient, hcrucible/copper melt 5000* W/(m2·K)
Interfacial heat transfer coefficient, hchiller/crucible 3000[24] W/(m2·K)
Interfacial heat transfer coefficient, hchiller/water 8000[25] W/(m2·K)
表1  温度场模拟中使用的参数值
图11  不同抽拉速率条件下模拟所得凝固界面形貌演化规律
图12  不同抽拉速率下模拟得到的平均凝固速率和理论计算的平均气孔孔径与实验值的比较
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