论文总字数：13879字

摘 要

梯度材料是一种新兴技术材料，梯度材料的主要特点是材料的结构组织要素会沿着切线方向呈连续性变化，梯度材料各方面的力学性能都很突出，在多种领域内都有广泛的运用，因此对于梯度材料的研究在国内外都十分热门，其中钛合金的表面强化问题一直是学者们讨论的热点话题。

本文主要研究内容是使用四点弯曲试验法探究钛合金表面渗氧强化后的各项指标，探究渗氧强化对钛合金表面的影响，先将TC4钛合金加工成试样并进行一定的预处理，再分别对试样进行间隙氧扩散和同等工艺真空时效处理。渗氧强化包括两个过程，首先是表面氧化，其次是氧扩散到钛合金基体中。 由于采用了一步法处理，氧化过程很容易发生，这避免了结垢和晶界扩散的发生。 尽管采取了这种预防措施，渗氧强化后材料的力学性能也会下降，这种情况被认为是表面氧化物团簇导致裂纹的产生。一般来说，固溶体中氧原子含量的增加可引起抗拉强度的增加，同时导致变形能力和延展性的下降。

对进行间隙氧扩散后的试样利用电解减薄工艺进行逐层减薄，同时采用X-RAY残余应力测试仪进行表面应力测量。为了得到开裂应变，采用OM观察开裂情况。为了验证四点弯曲实验的可靠性，采用有限元分析软件，模拟挠度和表面应变的关系及应变和应力的关系。

关键词：梯度材料 四点弯曲 钛合金 表面强化 渗氧

ABSTRACT

Gradient material is a new technology, the main characteristic of gradient material is the structure of the organizational elements will be a continuous variation along the tangent direction, all aspects of the mechanical properties of gradient materials are all very outstanding, it has been widely used in many fields, so the research on gradient materials is very popular at home and abroad, and the surface strengthening of titanium alloy has been a hot topic.

The main research content of this paper is to use the four-point bending test to explore the indicators of oxygen-enriched titanium alloy surface and the effect of oxygen-enriched titanium alloy surface. TC4 titanium alloy was processed into samples for pretreatment to a certain extent, and then the samples were subjected to the same process of gap oxygen diffusion and vacuum aging. The oxygen permeation enhancement includes two processes, the first is surface oxidation, the second is oxygen diffusion into the Titanium Alloy Matrix. The oxidation process is easy to occur because of the one-step treatment, which avoids scaling and Grain Boundary Diffusion. In spite of this precaution, the mechanical properties of the material strengthened by oxygen permeation also decrease, which is considered to be caused by surface oxide clusters. Generally speaking, the increase of oxygen atom content in solid solution can lead to the increase of tensile strength and decrease of deformation ability and ductility.

The specimens after interstitial oxygen diffusion were thinned layer by layer by electrolysis, and the surface stress was measured by X-RAY residual stress Tester. In order to get the cracking strain, the cracking condition was observed by OM. In order to verify the reliability of the four-point bending test, the relationship between deflection and surface strain and between strain and stress is simulated by the finite element analysis software.

KEYWORDS: Gradient Materials, four-point Bending, titanium alloy, surface strengthening, oxygen permeation

目录

摘 要 II

ABSTRACT III

第一章 绪论 1

1.1引言 1

1.2梯度材料起源和发展 1

1.3钛合金的表面强化 2

1.4四点弯曲实验法 4

1.5本文的主要研究内容 4

第二章 四点弯曲法 6

2.1试样制备与预处理 6

2.2 电解减薄工艺参数的确定 7

2.3四点弯曲实验 8

第三章 数据分析 10

3.1 原始材料电解减薄工艺探索 10

3.2 金相组织观察 12

3.3 氧扩散后电解减薄工艺 13

3.4四点弯曲实验 14

第四章 经济效益评价 19

第五章 总结 20

5.1 四点弯曲实验技术总结 20

5.2技术总结 21

参考文献 23

致谢 24

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