摘要钛铝基合金的本质脆性限制了其工业化应用，而定向凝固技术可控制晶粒取向，从而提高钛铝合金塑性，可获得综合性能良好的钛铝基合金。

利用感应悬浮熔炼制备Ti-45Al-6Nb合金铸锭，通过感应熔炼吸铸得到Ti-45Al-6Nb合金试棒；在刚玉坩埚内表面涂覆Y2O3惰性涂层，减少高温钛铝合金熔体与坩埚的反应；设计定向凝固感应加热线圈用来熔化Ti-45Al-6Nb合金试棒；通过W-Re5/26热电偶控制定向凝固时合金熔体的保温温度。67816

定向凝固Ti-45Al-6Nb合金试棒沿抽拉方向存在四个区域：铸态区、退火区、竞争生长区、稳定生长区，其中稳定生长区由柱状晶组成，晶粒内片层取向与抽拉方向成0º及45º左右夹角的占大多数，少数与抽拉方向垂直。Ti-45Al-6Nb合金在保温温度1550℃下，抽拉速率5µm/s时，合金初生相为β相，能得到较好的定向凝固组织。得到的定向凝固Ti-45Al-6Nb合金试棒中Al含量略低于原材料配比的Al含量(45at.%)，同时含有少量的Y2O3杂质，在稳定生长区中含有一定数量的横向晶界。

毕业论文关键词：Ti-45Al-6Nb合金，定向凝固，片层取向，微观、宏观组织

毕业设计说明书（论文）外文摘要

Title  On the relationship between TiAl alloy lamellar orientation and pulling velocity

Abstract

However,because of the brittle of TiAl alloy limit its industrial application.Directional solidification technique can control the grain orientation,and improve the plastic of TiAl alloy.This method can improve the comprehensive Performance of TiAl alloy.

First,using induction melting to prepare Ti-45Al-6Nb  alloy ingot and Ti-45Al-6Nb alloy bar.Second,the bars were placed into alumina crucibles coated with Y2O3 , which can reduce the reaction between melting alloy and crucible. Third,designing appropriate induction heating coil for the directional solidification. Finally,we use a W-Res/26 thermocouple to test the heat preservation temperature.

The macroscopic structure of directional solidified Ti-45Ai-6Nb bar shows four regions:casting region,directional anneal region, competition growing region and directional solidified region.Directional solidified regions are composed by columnar crystal.The lamellar orientation is shown in the columnar crystal.There are certain angle between most of lamellar orientation and the pulling direction,a few of lamellar orientation parallel or vertical to the pulling direction.At the holding temperature of 1550℃ and a pulling velocity of 5µm/s,Ti-45Al-6Nb alloy can get a better directional solidification organization.The primary phase is β.And there is a β single-phase in the process of solidification.

Keywords： Ti-45Al-6Nb alloy,Directional solidification,Lamellar orientation,Pulling velocity

目   次

摘  要 I

Abstract II

目次 IV

1 引言 1

1.1 研究背景 1

1.1.1 TiAl合金的基本性能 1

1.1.2 合金化元素对TiAl合金性能的影响 2

1.1.3 TiAl合金的制备技术现状 3

1.1.4 TiAl 合金的应用 4

1.2 TiAl基合金组织结构 5

1.3 研究现状 7

1.3.1 Ti-45Al-6Nb合金的性能特点 8

1.3.2 Ti-45Al-6Nb合金的定向凝固制备 8

1.4 本论文研究内容