摘要TiAl合金无论是在使用温度、高温强度、高温抗蠕变还是抗氧化等性能上都表现优异，但是钛铝合金的本质脆性限制了其工业化应用。经研究发现定向凝固可控制晶粒取向，从而可以提高钛铝合金塑性。67171

通过感应熔炼制备TiAl合金钮扣锭以及吸铸得到TiAl合金试棒,控制保温温度及抽拉速率不变，定向凝固得到柱状晶组织。研究Nb元素的添加对定向凝固TiAl基合金组织的影响。实验发现，当保温温度和抽拉速率相同时，Ti-45Al合金的晶粒随着Nb元素的添加而粗化，柱状晶长轴与生长方向更趋近于平行，同时液固界面组织发生变化。 

毕业论文关键词： TiAl合金，定向凝固，Nb元素，晶粒粗化，柱状晶，液固界面

毕业设计说明书（论文）外文摘要

Title  The reserch of the liquid-solid interface microstructure of TiAl alloy’s directional solidification 

Abstract

TiAl alloy can be used at high temperature, and it also has other excellent performance, such as oxidation resistance,tensile strength and creep strength at elevated temperature. But the brittle of TiAl alloy limit its industrial application.Some studies found that directional solidification technique can control the grain orientation,and improve the plastic of TiAl alloy.

This experiment uses induction smelting and suction casting to prepare TiAl alloy ingot and get TiAl alloy bar. Keep the heating temperature and the pull rate unchanged, columnar crystal can be got by directional solidification, and the effects of element Nb were investigated in the TiAl alloy. It was found that at the same heat preservation temperature and the same pulling rate, with the increase of the content of element Nb, the size of Ti-45Al alloy's crystal reduces, and the angle of the columnar crystals and direction of growth becomes more and more parallel. Meanwhile liquid-solid interface structure changes.

Keyword: TiAl alloy, directional solidification, element Nb   

         grain enlargement, columnar crystals, liquid-solid interface

目 录

1  引言 1

1.1  课题研究背景 1

1.2  TiAl基合金的组织结构 1

1.3  TiAl基合金的研究发展趋势 3

1.4  本课题研究内容 5

2  实验方法 6

2.1  实验方案 6

2.2  实验材料及设备 6

2.2.1  实验材料 6

2.2.2  实验设备 6

2.3  实验过程 10

2.3.1  钛铝合金钮扣锭的制备 10

2.3.2  吸铸得到钛铝合金试棒 11

2.3.3  钛铝合金试棒的定向凝固 12

2.4  分析方法 13

3  实验结果分析及讨论 14

3.1  实验结果 14

3.2  分析及讨论 16

3.2.1  晶粒粗化机理 16

3.2.2  片层间距细化机理 16

3.2.3  片层取向不同的原因 16

3.2.4  固液界面组织讨论