论文总字数：23040字

摘 要

钛合金以其优异的比强度、热强度、抗腐蚀性、低温性能、机械性能等成为新型海工钢筋的优选材料。本课题主要研究TF400钛合金在锻压开坯及精锻开坯两种不同工艺下外缘、中部及芯部各部位的微观组织变化、力学性能和电化学腐蚀行为。通过实验能够分析得出快锻TF400不同部位的显微组织相近，具有较好的均匀性，都为等轴组织，而精锻TF400各部位组织形态变化明显，其中边缘组织类似于等轴组织，中部组织主要为片层和少量网篮状分布，芯部组织主要呈现为网篮状交错分布。精锻TF400钛合金边缘和芯部区域的α相宽度与快锻TF400钛合金相差不大，但精锻TF400钛合金中部α相宽度(8.75μm)较快锻TF400钛合金中部α相宽度(11.86μm)小。微观组织上的变化在力学性能上的表现为：精锻TF400钛合金的强硬度优于快锻TF400钛合金，但其塑韧性较低；在电化学腐蚀性能上的表现为：精锻TF400钛合金的边缘区域耐蚀性能最好，而快锻TF400钛合金中部的组织耐蚀性能最差；快锻TF400钛合金棒材的耐点蚀性能优于精锻TF400钛合金，但当棒材轧制成钢筋后，不论是快锻钢筋还是精锻钢筋，耐点蚀性都提高了。

关键词：开坯工艺 TF400钛合金 微观组织 力学性能 电化学腐蚀行为

Effect of Cogging Processes on Microstructure, Mechanical Properties and Electrochemical Corrosion Behavior of TF400 Marine Rebar

Abstract

Titanium alloy has become the preferred material for new marine engineering reinforcement because of its good strength-to-weight ratio, thermal strength, corrosion resistance, low temperature performance and mechanical properties. This paper mainly studies the microstructural changes, mechanical properties and related electrochemical corrosion behavior of the surface, middle part and core part of TF400 titanium alloys under two different cogging processes of traditional cogging and new cogging. Through the experiments, it can be found that the microstructure of different parts of the traditional cogged TF400 is similar and has good uniformity, all of which are equiaxed. But the microstructure of the parts of new cogged TF400 changed obviously. The surface is similar to the equiaxed structure. The middle is mainly distributed by the lamellar and a few basket-weave . The core is mainly appeared as basket-weave. The α phase width of the edge and core region of the new cogged TF400 titanium alloy is not much different from that of the traditional cogged TF400 titanium alloy, but the width of α phase in the middle of new cogged TF400 titanium alloy (8.75 μm) is smaller than that in the middle of traditional cogged TF400 titanium alloy (11.86 μm). The mechanical properties related to the microstructures are as follows: the strength and hardness of new cogged TF400 titanium alloys are better than that of traditional cogged TF400 titanium alloys, but their plastic toughness is lower. By studying the electrochemical corrosion properties related to the microstructures, the surface of new cogged TF400 titanium alloy has the best corrosion resistance, while that of the middle part of traditional cogged TF400 titanium alloy is the worst. The pitting corrosion resistance of traditional cogged TF400 titanium alloy bar is better than that of new cogged TF400 titanium alloy. But when the bar is rolled into rebar, the pitting corrosion resistance of both traditional cogged rebar and precision cogged rebar is improved.

Key words: cogging processes; TF400 titanium alloys; microstructure; mechanical properties; electrochemical corrosion behavior

目录

摘 要 I

Abstract II

目录 III

第一章 绪论 1

1.1引言 1

1.2钛及钛合金介绍 1

1.2.1钛的基本属性 1

1.2.2钛合金及其组织分类 2

1.3合金元素对钛合金的影响 3

1.3.1 Fe元素对钛合金的影响 3

1.3.2 B元素对钛合金的影响 3

1.4 锻造温度对钛合金组织及性能的影响 4

1.5 选题意义、目的及研究内容 4

第二章 实验材料及方法 6

2.1 实验材料 6

2.1.1实验仪器与药品 6

2.2 实验方案 7

2.3 实验方法 8

2.3.1 金相组织观察和分析 8

2.3.2 力学性能实验 8

2.3.3 电化学实验 10

第三章 结果与分析 12

3.1 快锻及精锻工艺对TF400钛合金微观组织的影响作用 12

3.2 力学性能测试 13

3.2.1 合金室温拉伸性能测试 13

3.2.2 合金维氏硬度测试 14

3.3电化学测试 15

3.3.1 电化学阻抗(EIS)实验结果 16

3.3.2极化曲线实验结果 19

3.3.3浸泡试验对两种锻造工艺下TF400钛合金的影响作用 21

第四章 结论和展望 24

4.1实验结论 24

4.2展望 25

参考文献 26

致 谢 29

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