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首页> 外文学位 >Microstructural development and mechanical properties of the vacuum plasma sprayed titanium-aluminum-vanadium alloy.
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Microstructural development and mechanical properties of the vacuum plasma sprayed titanium-aluminum-vanadium alloy.

机译：真空等离子喷涂钛铝钒合金的显微组织发展和力学性能。

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摘要

Recently, vacuum plasma spray forming (VPSF) has been identified as a process capable of manufacturing near-net-shape components for advanced technology applications such as aerospace, defense, and chemical process industries. By optimizing the deposit structure via intelligent control of process parameters and utilizing post-deposition heat treatments, deposit structures with properties better than conventionally cast materials and, in some cases, equivalent to wrought materials can be produced.; In the current study, one of the most important and widely used titanium alloys, Ti-6Al-4V, was chosen to form a near-net-shape structure by VPSF process. The microstructure and properties of the initial powder and the as-deposited component were characterized. It was found that the as-deposited material consisted of approximately 90% martensite present in the form of fine lathes (∼500 nm in width), being surrounded by a residual beta phase. The as-sprayed material failed at low elongations (∼1%) when tested in tension. The fundamental basis of the relationships between the physical and mechanical properties and the as-sprayed microstructure was elucidated. To provide insight into the deposition, the solidification behavior and morphology of a single splat of Ti-6Al-4V alloy deposited under VPSF conditions were investigated using both numerical simulation and experimental observations. The average cooling rate and solidification front velocity were found to be approximately 6x108 °C/sec and 63 cm/sec, respectively. A mechanistic model for the relationship between the elastic modulus and the thermally sprayed microstructure was developed and compared with the results of an image based finite element method (OOF) and in-situ tensile testing.; To study the response of the as-sprayed structure to heat treatment cycles, the mechanisms of grain growth and pore elimination (densification) were investigated in detail. Then, three heat treatment cycles were developed and successfully applied to the as-sprayed structure. The level of porosity in the heat treated materials reduced as low as 1% and the ductility were markedly improved (∼10%) by all heat treatments. The Young's modulus of the heat treated structures was improved (115--120 GPa) significantly and was close to those of wrought heat treated materials.
机译：最近，真空等离子喷涂成型（VPSF）已被确认为一种能够制造用于航空航天，国防和化学加工工业等先进技术应用的近净形部件的工艺。通过对工艺参数的智能控制来优化沉积结构，并利用沉积后热处理技术，可以生产出性能优于传统铸造材料并且在某些情况下可以等同于锻造材料的沉积结构。在当前的研究中，最重要且用途最广泛的钛合金之一Ti-6Al-4V被选择通过VPSF工艺形成近净形结构。表征了初始粉末和所沉积的组分的微观结构和性能。已发现，沉积态的材料由大约90％的马氏体组成，以细车床的形式存在（宽度约为500 nm），被残留的β相包围。当进行拉伸测试时，喷涂后的材料在低伸长率（约1％）时失效。阐明了物理和机械性能与喷涂态微观结构之间关系的基本基础。为了提供对沉积的了解，使用数值模拟和实验观察方法研究了在VPSF条件下沉积的单片Ti-6Al-4V合金的凝固行为和形态。发现平均冷却速率和凝固前沿速度分别为约6×108℃/秒和63cm /秒。建立了弹性模量与热喷涂微观结构之间关系的机械模型，并将其与基于图像的有限元方法（OOF）和原位拉伸测试的结果进行了比较。为了研究喷涂结构对热处理周期的响应，详细研究了晶粒生长和孔消除（致密化）的机理。然后，开发了三个热处理周期，并将其成功应用于喷涂后的结构。热处理后的材料中的孔隙率降低至1％，而所有热处理均显着改善了延展性（约10％）。热处理结构的杨氏模量显着提高（115--120 GPa），接近锻造热处理材料的杨氏模量。

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  • 作者

    Salimijazi, Hamidreza.;

  • 作者单位

    University of Toronto (Canada).;

  • 授予单位 University of Toronto (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 196 p.
  • 总页数 196
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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