高Nb-TiAl合金定向凝固组织片层取向研究
关键词 高Nb-TiAl合金 定向凝固 生长速率 片层取向
毕业设计说明书（论文）外文摘要
Title Control of high Nb-TiAl alloy lamellar orientation in Directional Solidification and Its mechanism.
Abstract
In this composition, Ti-45Al-8Nb alloy, as the object of study, was directional solidified at 10μm / s, 15μm / s and 20μm / s growth rate respectively. And then discussed the influence of growth rate on Nb-TiAl alloy lamellar orientation as well as its control mechanism. We obtain single crystals at the growth speed of 10μm / s and 15μm / s, and both the alloy lamellar orientation were nearly 70°as to the growth direction. However, when the alloy was directional solidified at 20μm / s, we failed to get single crystals as it contains two different lamellar orientation, 45°and 60°. We find that growth rate and temperature gradient have great impact on the final microstructure in directional solidification. Consequently, according to data of the experiment, we analyzed and discussed reasons contributing to what we talked above and hope to provide some valuable information for the next work.
Keywords high Nb-TiAl alloy directional solidification growth speed
lamellar orientation
目录
1 引言 1
1.1 选题意义 1
1.2 TiAl基合金定向凝固技术及其研究现状 2
1.2.1 TiAl合金组织与力学性能 2
1.2.2 TiAl合金相图 4
1.2.3 定向凝固技术 5
1.3 高Nb-TiAl合金的研究现状 8
1.3.1 Nb元素对TiAl相图的影响 8
1.3.2 高Nb-TiAl合金高温性能 10
1.3.3高Nb-TiAl合金定向凝固的研究 11
1.4 本实验主要研究内容 12
1.5 本章小结 12
2 实验过程 13
2.1 实验的材料与试样的制备方法 13
2.1.1 真空电弧熔炼制备母合金 14
2.1.2 真空吸铸 14
2.2 试样的定向凝固 15
2.3金相观察与处理 17
3 试验结果与分析讨论 18
3.1 抽拉速率对定向凝固组织的影响 18
3.2定向凝固方式对凝固组织的影响 23
3.3未得到与生长方向平行的全片层组织的原因 25
3.3.1初生相出现了α相 26
3.3.2 β相晶体择优生长被破坏 27
3.3.3 铸态原始组织的引晶作用的影响 28
3.3.4 界面能的影响 28
3.4 本章小结 28
4 结论 29
5 致谢 30
参 考 文 献 31