论文总字数：24023字

摘 要

钛及钛合金作为一种结构材料以其优异的物理性能和良好力学性能在航空航天及机械工业领域有着不可或缺的作用，并且广泛应用于诸多其他领域。由于钛及钛合金的快速应用及发展已经是一个全新的方向，因此对于钛及钛合金零件性能全面提升和复杂结构件可靠制造性将对未来钛合金制造业具有非常重要的意义。电弧增材制造技术采用设计好的系统程序控制机器按照路径逐层堆积焊接的加工方式制造致密金属合金结构件，以电弧为载能束，热输入量高、成形准确速度快、低成本，适用于大尺寸复杂合金结构件。但由于成型合金内部组织粗大，严重影响了合金零件的综合性能及实际应用上。本课题将通过对钛合金电弧增材制造的合金进行置氢处理新思路，实现钛合金结构件的组织细化和综合性能提升。

本课题在电弧增材制造过程中，对钛合金焊丝进行置氢处理，利用置氢钛合金焊丝在打印过程中基于氢的熔化与凝固过程中氢化物的析出与分解促进熔池内的形核及成分过冷多方面促进形核，再通过真空退火将临时合金化元素氢除去，避免最终材料的化学成分的改变，同时利用氢在过程中细化改善打印件组织，并且达到改善组织不改变合金成分的目的，有望为承力结构件性能全面提升和复杂结构件可靠制造提供理论指导。

实验结果表明：当氢含量在0.4wt%时，TC4钛合金中马氏体较粗大，由等轴组织转变为条状组织，且位错增多。TC4钛合金经850℃淬火后，初生α相开始生长，在高温淬火工艺下，冷却速度极快，使得初生α相的再结晶停止，片状α相组织粗化且不均匀，这会使得材料综合性能不均一，降低材料塑性；TC4钛合金经淬火850℃再在热处理炉600℃保温2小时得到的针状α相组织较为粗大一些，其网篮组织也更加致密，整体组织相对均匀，材料综合性能均一，增加结构件材料塑性。室温下，TC4钛合金随含氢量的增加而提高强度，降低塑性。

关键词：电弧增材制造；TC4钛合金；置氢处理；显微组织；力学性能

Study on Microstructure and Properties of Arc Additive Manufacturing of Hydrogenated Titanium Alloy Welding Wire

Abstract

As a structural material, titanium and titanium alloys play an indispensable role in the aerospace and mechanical industry due to their excellent physical properties and good mechanical properties, and are widely used in many other fields. Since the rapid application and development of titanium and titanium alloys is a new direction, it is of great significance for the future titanium alloy manufacturing industry to comprehensively improve the performance of titanium and titanium alloy parts and to reliably manufacture complex structural parts. The arc additive manufacturing technology adopts a designed system program to control the machine to manufacture dense metal alloy structural parts according to the processing method of layer-by-layer stacking welding. The arc is used as the energy beam, which has high heat input, accurate forming speed, low cost, and is applicable. For large-size complex alloy structural parts. However, due to the thick internal structure of the forming alloy, it seriously affects the comprehensive performance and practical application of the alloy parts. This subject will realize the refinement of the structure of titanium alloy structural parts and the improvement of overall performance through the new idea of ​​hydrogen treatment of alloys manufactured by titanium alloy arc additive.

In this topic, in the process of arc additive manufacturing, the titanium alloy welding wire is subjected to hydrogen treatment. The hydrogen-based titanium alloy welding wire is used to promote the nucleation and nucleation in the molten pool during the hydrogen-based melting and solidification of the hydrogenation welding wire during printing. The supercooling of the composition promotes nucleation in many ways, and then the temporary alloying element hydrogen is removed by vacuum annealing to avoid the change of the chemical composition of the final material. At the same time, the hydrogen is used to refine the print structure during the process, and the improved structure does not change the alloy. The purpose of the composition is expected to provide theoretical guidance for the comprehensive improvement of the performance of load-bearing structural parts and the reliable manufacture of complex structural parts.

The experimental results show that when the hydrogen content is 0.4wt%, the martensite in the TC4 titanium alloy is coarser and changes from an equiaxed structure to a strip structure with increased dislocations. After the TC4 titanium alloy is quenched at 850℃, the primary α phase begins to grow. Under the high temperature quenching process, the cooling rate is extremely fast, so that the recrystallization of the primary α phase stops, and the flake α phase structure is coarse and uneven, which will make the material The overall performance is not uniform, which reduces the plasticity of the material; the needle-like α-phase structure obtained by quenching TC4 titanium alloy at 850 ℃ and then holding at 600 ℃ for 2 hours is coarser, the mesh basket structure is also denser, the overall structure is relatively uniform, and the material The overall performance is uniform, increasing the plasticity of the structural material. At room temperature, TC4 titanium alloy increases strength and decreases plasticity with increasing hydrogen content.

Keywords: arc additive manufacturing; TC4 titanium alloy;hydrogen treatment; microstructure; mechanical properties

目录

摘要 I

Abstract II

第1章 绪 论 1

1.1课题来源 1

1.2课题研究背景 1

1.3钛及钛合金简介 2

1.3.1钛及钛合金 2

1.3.2钛合金的分类及特点 2

1.4电弧增材制造技术 3

1.4.1电弧增材制造技术概述 3

1.4.2电弧增材制造技术研究现状及展望 4

1.5氢在钛合金中的作用 5

1.5.1氢在钛及钛合金中的特性 5

1.5.2氢在钛及钛合金的作用原理 6

1.5.3置氢处理对TC4钛合金的影响 6

1.6课题研究目的及意义 7

1.7本文主要的研究内容 7

第2章实验材料与方法 9

2.1引言 9

2.2实验材料及设备 9

2.2.1实验材料 9

2.2.2电弧增材制造系统 9

2.2.3钛合金置氢系统 12

2.3组织性能分析方法 12

2.3.1电弧增材制造TC4钛合金显微组织分析 12

2.3.2电弧增材制造TC4钛合金力学性能分析 13

第3章置氢电弧增材制造TC4钛合金工艺试验 15

3.1引言 15

3.2电弧增材制造工艺研究 15

3.2.1单道单层试验 15

3.2.2多道多层试验 17

3.3置氢工艺 18

3.4置氢-除氢钛合金电弧增材制造微观组织分析 19

3.4.1置氢TC4钛合金微观组织分析 19

3.4.2置氢TC4钛合金淬火后的微观组织分析 20

3.4.3除氢TC4钛合金微观组织分析 21

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