| Al-Mg合金焊缝金属晶粒细化的形核机制 | |
| 施成根 | |
| Subtype | 硕士 |
| Thesis Advisor | 陈晓风 |
| 1991 | |
| Degree Grantor | 中国科学院金属研究所 |
| Place of Conferral | 中国科学院金属研究所 |
| Abstract | 电子束摆动焊接Al-Mg合金表明：随着摆动频率的提高，焊缝金属晶粒细化程度增加，对应的维氏硬度和抗拉强度增加。当摆动频率为300Hz时，焊缝金属晶粒全部转变为细小的“等轴晶”，相应的焊缝金属维氏硬度和抗拉强度达到最大值，与无摆动电子束焊接相比，焊缝金属抗拉强度提高50％接近母材。随着摆动频率继续增高，焊缝金属晶粒开始粗化。对应焊缝金属维氏硬度和抗拉强度也开始下降。本文讨论了焊接熔池固液界面前沿组成过冷度与电子束摆动频率之间关系，熔切表面基底能量、晶体结构取向与电子束摆动频率之间的关系，指出：摆动频率为300Hz时，对应基底形核的必要能量与充要能量之和为2.2 * 10~(-3J)，即是非均质形核的临界能量。摆动电子束焊接时，界面组成过冷能量（形核的必要能量）与基底界面自由能（形核的充要能量）之和等于或大于非均质形核的临界能量，基底就可形核，晶粒细化。当摆动频率大于300Hz时，则基底不能形核。只有电子束多次熔切使基底能量增高达到非均质形核的临界能量时，在长大的晶体表面上形核，晶粒开始粗化。 |
| Other Abstract | The vibration of electron beam welding of Al-Mg alloy shows that with increasing of vibrating frequency the size of the grain in the weld metal is decreased, the hardness and the tensile strength of the weld metal are increased. When the vibrating frequency is 300Hz, the columnar grain in the weld metal is all changed into the fine equi-axed grain, the hardness and the tensile strength are the maximun. The tensile strength of the weld metal is increased by 50 Percent than that of which with no vibrating technique, and it is very close to that of base metal. Along with the more increasing of vibrating frequency, the size of the grain in the weld metal is getting larger, the hardness and the tensile strength of the weld metal are becoming lower. In this paper, the relationship between the constitutional supercooling in front of the solid-liquid interface in the weld pool and the vibrating frequency of electron beam, the relationship between the surface energy on the substrate, the diraction of the crystal structure and the vibrating frequency of electron beam are studied. The vibrating frequency of electron beam is 300Hz, the sum of the essential energy and the resonal energy of heterogenous nucleation is 0.0022J. This is the critical energy of heterogenous nucleation on the substrate. When the vibration of EBW is used, and the sum of the energy of the interface, which is the essential energy of heterogenous nucleation, and the active energy on the substrate, which is the resonal energy of heterogenous nucleation, are equal or over the critical energy of heterogenous nucleation, then heterogenous nucleation will occur on the substrate, and the grain in the weld metal will be refined. When the vibrating frequency is over 300Hz, heterogenous nucleation will not occur on the substrate. Only when the energy of the surface on the substrate adds up to the critical energy of heterogenous nucleation by electron beam vibration, will heterogenous nucleation occur on the grown grain surface. The size of the grain in the weld metal is becoming bigger. |
| Pages | 57 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.imr.ac.cn/handle/321006/17529 |
| Collection | 中国科学院金属研究所 |
| Recommended Citation GB/T 7714 | 施成根. Al-Mg合金焊缝金属晶粒细化的形核机制[D]. 中国科学院金属研究所. 中国科学院金属研究所,1991. |
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