论文总字数：18477字

摘 要

本课题以新型低成本合金Ti-Fe-B为研究对象，采用金相显微镜（OM）、热分析仪（DSC）、X射线衍射仪（XRD）、拉伸试验机等分析测试手段，系统地研究了双重退火工艺（810℃，1h，空冷 530℃，1h，空冷）对Ti-Fe-B合金的组织和力学性能的影响。研究结果表明：

（1）Ti-Fe-B为典型的（α β）双相钛合金，热轧态初始试样微观组织主要由片层α相和晶间β相组成，经过双重退火处理后，试样微观组织主要由条状和球状的初生α相、次生α相和少量亚稳β相组成，通过XRD分析可知，试样经双重退火后，α相含量由初始态的63.02%增加到85.64%，另一方面，β相含量由36.98%减少到14.36%；

（2）经双重退火热处理后，Ti-Fe-B合金的抗拉强度由原来的705MPa降低到644MPa，另一方面，其断后伸长率由原来的18.0%提高到21.0%，这主要是由于钛合金的增强相β相含量的大幅减少，且提升强度的相组织球状α相分布较少，合金基体中更多的是网篮状的α相——网篮状组织可以有效提高合金的韧塑性。通过断口形貌的分析发现：双重退火前后试样都呈现韧窝断裂形貌，对比发现，双重退火后试样的韧窝比初始试样更多、更均匀和密集，表明Ti-Fe-B合金经过双重退火后较为良好的综合力学性能。

关键词：Ti-Fe-B合金；双重退火；组织；力学性能

Effect of Double Annealing on Microstructure and Mechanical Properties of Ti-Fe-B Alloy

Abstract

In this study, the new low-cost alloy Ti-Fe-B was used as the research object, and analyzed by metallographic microscope (OM), thermal analysis (DSC), X-ray diffraction (XRD), tensile testing machine and so on. The effects of double annealing (810 ℃, 1h, air cooling 530 ℃, 1h, air cooling) on the microstructure and mechanical properties of Ti-Fe-B alloy were studied. This research indicates:
(1) Ti-Fe-B is a typical (α β) biphasic titanium alloy. The microstructure of hot sample is mainly composed of lamellar α phase and intergranular β phase. After double annealing, the microstructures of the samples consist mainly of the primary α-phase, the secondary α phase and the small metastable β phase. By XRD analysis , the results show that the content of α phase increases from 63.02% to 85.64% in the initial state after double annealing. On the other hand, β phase decreases from 36.98% to 14.36%;
(2) After the double annealing heat treatment, the tensile strength of Ti-Fe-B alloy decreased from 705MPa to 644MPa. On the other hand, the elongation at break increases from 18.0% to 21.0%, which is mainly due to Titanium alloy reinforced phase β phase content of a substantial reduction. Besides, enhance the intensity of the phase structure of the spherical α-phase distribution is less, and the alloy matrix is more basket-like α phase —basket-like organization can effectively improve the toughness of the alloy Plasticity. The results show that the ductile fissures of the samples are more、more uniform and dense than that of the initial samples after double annealing, which indicates that the Ti-Fe-B Alloy has a good comprehensive mechanical property after double annealing.

Key words: Ti-Fe-B alloy; double annealing; microstructure; mechanical properties

目 录

摘要 I

Abstract II

第一章 绪论 1

1.1 概述 1

1.2 钛合金的分类及组织种类 2

1.3 合金元素对钛合金的作用 4

1.3.1 Fe元素对钛合金的作用 5

1.3.2 B元素对钛合金的作用 5

1.4 钛合金热处理工艺 5

1.5 选题意义、目的及研究内容 6

第二章 实验材料和方法 7

2.1 实验材料 7

2.2 实验方案 7

2.3 实验方法 7

2.3.1 DSC实验 7

2.3.2 热处理试验 8

2.3.3 组织观察和分析 9

2.3.3.1 金相组织观察 9

2.3.3.2 XRD物相分析 10

2.3.4 力学性能实验 11

2.3.4.1 拉伸性能实验 11

2.3.4.2 硬度实验 13

2.3.5 扫描电子显微镜观察 13

第三章 双重退火工艺对Ti-Fe-B合金组织和力学性能的影响 14

3.1 Ti-Fe-B合金热处理前后XRD物相分析 14

3.2 Ti-Fe-B合金热处理前后微观组织形貌 15

3.3 双重退火工艺对Ti-Fe-B合金组织的影响 16

3.4力学性能测试 16

3.4.1 合金室温拉伸性能测试 17

3.4.2 拉伸断口形貌分析 18

3.4.3 合金维氏硬度测试 19

3.5 本章小结 19

第四章 结论和展望 21

参考文献 23

致 谢 24

第一章 绪论

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