论文简介：

毕业论文-二维放射状Gasar多孔镁制备工艺研究，共70页，26282字
摘要
金属/气体共晶定向凝固（Gasar）作为一种制备规则多孔金属的新型工
艺备受关注。当沿径向凝固时，用 Gasar 工艺制得的多孔材料呈现二维放射
状规则排列。该种多孔材料在过滤器、自润滑轴承以及燃油喷注器、气体分
散器等功能性装置方面具有潜在应用。本文利用所在实验室的 Gasar 装置，
开展了有关二维放射状多孔金属 Mg 的制备工艺研究。
所得实验结果从横截面上看，基本上呈现出二维放射状规则排列的多孔
结构，但是气孔分布仍然存在一定程度上的紊乱。
通过对各种条件下的实验结果的分析，揭示了气体压力对气孔率和气孔
尺寸的影响规律。使用单一氢气时，随着氢气压力的增大，气孔率降低，气
孔平均直径减小；当氢气压力一定时，随着氩气压力的增大，气孔率、气孔
平均直径也呈现出相同的变化规律。通过加入氩气提高附加压力，可以有效
的阻止气泡溢出，使实验所得气孔率和预期值相吻合。
采用商用 CFD 软件对充型过程进行数值模拟，表明顶注法不利于二维放
射状规则镁金属的制备。顶注法在充型过程中造成比较紊乱的流动，最终使
气孔的分布呈现出一定程度上的混乱，同时还带来卷气造成大气孔缺陷。
关键词：金属/气体共晶，定向凝固，多孔材料，放射状结构，充型过程模拟

ABSRTACT
Unidirectional solidification of metal-gas eutectic, also called “Gasar”
process, is regarded as a revolutionary method for fabricating porous metals. The
porous structure with radial pores distribution can be obtained by the radial
unidirectional solidification. This kind of porous structure possesses wide
potential applications as filters, self-lubricated bearings, fuel sprayers and gas
distributors. By use of the developed Gasar apparatus, this thesis successfully
fabricated Gasar magnesium with radial pores distribution and investigated the
effects of processing parameters on the final porous structure.
The experimental results and the theoretical analysis show that the gas
pressure has a significant effect on the porosity and average pore size. When only
hydrogen is used, the porosity and the average pore size decrease with increasing
hydrogen pressure. When the mixture of hydrogen and argon is used and the
partial pressure of hydrogen keeps constant, the porosity and the average pore
size decrease with increasing partial pressure of argon. The addition of argon can
prevent the hydrogen from escaping from the melt during the solidification
process, and reduce the error between the measured results and the theoretically
predicted values.
The numerical simulation of the mold filling by the commercial CFD
software shows that the top-filling mode is not in favor of the fabrication of the
radial porous metals, because that the turbulent fluid flow causes a
non-homogeneous temperature distribution, therefore leads to a disorder
distribution direction of pores. In addition, the turbulent fluid flow also causes
other defects such as the big wrapped blow holes.
Key Words: Metal/gas eutectic, Unidirectional solidification, Porous material,
Radial porous structure, Simulation of mold filling

目录
第一章 引言 ..... 1
1.1 选题背景... 1
1.2 文献综述... 3
1.2.1 Gasar 工艺原理 3
1.2.2 气泡形核理论 ... 5
1.2.3 金属/气体共晶生长动力学[3] ..... 6
1.2.4 藕状状 Gasar 材料的制备及工艺参数的影响 ..... 7
1.3 GASAR 工艺的发展现状及存在的问题 ....... 13
1.4 本文研究目的及内容........ 14
第二章 实验材料及研究方法 .... 16
2.1 实验装置. 16
2.2 制备工艺. 17
2.3 工艺方案及实验参数选择 18
第三章 实验结果及分析 ... 19
3.1 引言 19
3.2 气孔率..... 19
3.3 气孔的分布...... 24
3.4 气孔的尺寸...... 29
3.5 本章小结. 31
第四章 充型过程模拟 ....... 32
4.1 引言 32
4.2 充型过程模拟.. 32
4.2.1 模型参数 32
4.2.2 充型过程模拟计算结果 ... 33
4.2.3 充型过程模拟结果分析 ... 39
4.3 本章小结. 41
结论 . 42
参考文献 .. 43
致谢 .... 45
声明 .... 45
附录 英文文献翻译 A ....... 46
附录 英文文献翻译 B ....... 52

论文文件预览：
共1文件夹，1个文件，文件总大小：5.97MB，压缩后大小：2.67MB

• 毕业论文-二维放射状Gasar多孔镁制备工艺研究
• 毕业论文-二维放射状Gasar多孔镁制备工艺研究.doc  [5.97MB]