文档介绍：Classified Index: TG454 :
Dissertation for the Master Degree in Engineering
RESEARCH ON ALUMINIZING ICS AND MICROSTRUCTURE OF FOIL-PACKED ALUMINIZED Ti-Al-V ALLOY SHEET
Candidate:
Li Yan
Supervisor:
Associate Prof. Li Mingwei
Academic Degree Applied for:
Master of Engineering
Speciality:
Materials
Affiliation:
School of Materials Science and Engineering
Date of Defence:
July, 2010
Degree-Conferring-Institution:
Harbin Institute of Technology
摘 要
钛合金具有重量轻、密度小、比强度高等优点,在航空航天等工业领域得到广泛的应用。但是,在高温下使用时钛合金的氧化和氧脆成为影响其热稳定性的主要因素。渗铝是提高钛合金的高温使用性能最有效的方法之一。本文采用铝箔包覆渗铝工艺,对电子束物理气相沉积(EB-PVD)制备的 Ti-Al-V 合金薄板进行渗铝处理,并对渗铝后的合金薄板进行热处理。采用光学金相显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)对 Ti-Al-V 合金薄板渗铝层截面的微观形貌和元素分布进行分析研究。采用纳米显微硬度计测试渗铝薄板的显微硬度。采用 X 射线衍射仪(XRD)对合金薄板的渗铝层及扩散层的相组成进行分析。
研究结果表明,EB-PVD制备的Ti-Al-V合金薄板的主相为α-Ti固溶体,其组织均匀致密,晶粒细小,无裂纹和宏观缺陷。合金薄板在 700℃、800℃和 900℃渗铝后,渗层的主相为Al 3 Ti,其中还有少量的Al2 Ti及TiAl相。渗层与基体之间的界面清晰平整,无过渡层。随着渗铝时间的延长,渗层与基体之间开始出现少量的互扩散,扩散区的界面清晰但不平整。渗层增厚动力学表明,渗层厚度随扩散温度的升高呈递增趋势,渗铝过程的动力学主要受Al在基体中的固态扩散所控制。渗铝层的纳米硬度约为 9GPa,弹性模量约为 200GPa,且硬度和模量在 50~500nm内不随压痕深度的变化而变化。
在 1000℃、1100℃下短时间热处理后,渗层与基体发生较多的互扩散,出现过渡层,层与层之间的界面清晰,1000℃热处理 4h后,渗层与基体之间的过渡层变薄,层与层之间的衬度变小,界面逐渐变得不平整。1100℃热处理 4h后, 渗层与基体之间的扩散区中出现了Ti的富集。1000℃热处理 3 Ti,随着热处理时间的延长,Al 3 Ti层逐渐变薄,最后消失。1100℃热处
理后渗层的主相为Al2 Ti和TiAl。
关键词:电子束物理气相沉积;Ti-Al-V 合金薄板;渗铝;热处理
Abstract
Titanium alloy has advantages such as light weight, low density, high specific strength and so on. It’s widely used in aerospace, aviation and many other industries. However, the oxidation and oxygen embrittlement of titanium alloy are major factors which influenced the thermal stability at high temperature. Aluminized is one of the most effective methods to improve the performance of titanium alloy at high temperature. The microstructure of the foil-pack aluminized Ti-Al-V alloys sheet fabricated by electron beam physical vapor deposition (EB-PVD) technology and treated at different temperatures were studied in this thesis. The cross-section m