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首页> 外文学位 >Thermohydrogen processing (THP) of titanium-(6)aluminum-(4)vanadium and titanium-aluminum alloys.
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Thermohydrogen processing (THP) of titanium-(6)aluminum-(4)vanadium and titanium-aluminum alloys.

机译：钛-（6）铝-（4）钒和钛铝合金的热氢处理（THP）。

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摘要

The microstructures, phases and phase transformations occurring in cast and Hot Isostatic Pressed (HIP'd) Ti-6Al-4V-H and the blended elemental (BE) TiAl-H systems were investigated.; In this work, the existing Ti-6Al-4V-H phase diagram was revised and the time-temperature-transformation (TTT) diagrams for beta-phase (isothermal) and martensite (quench plus aging) decomposition were determined at different hydrogen concentrations. Alloying with hydrogen decreases the nose temperatures for the start of both the beta/martensite decompositions in a linear fashion and increases the nose times for both of these in a non-linear fashion. During aging at temperatures below the beta transus temperature, the martensite decomposes into α+βM (metastable beta) and on quenching, from the aging temperature, the βM transforms to martensite + β R (residual beta) with the amount of latter increasing with increasing hydrogen content. Microstructures varying from α-lamellar laths to fine equiaxed α-grains were produced in the Ti-6Al-4V alloy, by using different thermohydrogen processing (THP) treatments. A microstructure consisting of mixed equiaxed and elongated α-grains were only produced in samples containing 30at.%H after the complete decomposition of the beta/martensite below a critical temperature (Tc), followed by dehydrogenation. A mixture consisting of partially equiaxed α-grains thus produced by THP, increased the tensile strength from 841MPa (starting Ti-6Al-4V) to 965MPa after THP and also increased the % elongation from 7.5% to 10.5%. In addition to other THP parameters, the final microstructure also depends on the starting microstructure and recommendations are made for future work in this regard. Initial results of temperature cycling treatments, which involved heat treating of Ti-6Al-4V samples containing 30at.%H at 680°C for 5 minutes followed by water quenching and repetition of the same treatment for 10 cycles, did not show a decrease in the average prior beta grain size; recommendations have been made for future work in this area.; Fully dense hydrogenated nano-crystalline TiAl compacts were produced from BE powders. HIP'ing of the mechanically alloyed hydrogenated powders at 850°C resulted in a homogenous microstructure, whereas prior powder particle boundaries were visible in the samples produced from non-hydrogenated powders. The hydrogen was removed by vacuum annealing resulting in nano-size γ-TiAl.
机译：研究了铸造和热等静压（HIP'd）Ti-6Al-4V-H和混合元素（BE）TiAl-H系统中的微观结构，相变和相变。在这项工作中，对现有的Ti-6Al-4V-H相图进行了修改，并确定了在不同氢浓度下β相（等温）和马氏体（淬火加时效）分解的时间-温度转变（TTT）图。与氢合金化以线性方式降低β/马氏体分解开始时的鼻温，并以非线性方式增加这两种分解的鼻温。在低于β转变温度的温度下进行时效过程中，马氏体分解为α+β M （可取代的β），淬火后，从时效温度开始，β M 转变为马氏体+β R （残余β），后者的含量随氢含量的增加而增加。通过使用不同的热氢处理（THP）处理，在Ti-6Al-4V合金中产生了从α片状板条到细等轴α晶粒的微结构。在临界温度（T ）下β/马氏体完全分解，然后脱氢后，仅在含30at。％H的样品中产生由混合的等轴和细长α晶粒组成的微观结构。由THP生成的部分等轴α晶粒组成的混合物，THP后的抗拉强度从841MPa（起始Ti-6Al-4V）提高到965MPa，并且伸长率百分比也从7.5％提高到10.5％。除了其他THP参数外，最终的微观结构还取决于初始微观结构，并针对此方面的未来工作提出了建议。温度循环处理的初步结果涉及在680°C下对含30at。％H的Ti-6Al-4V样品进行5分钟的热处理，然后用水淬灭并重复相同的处理10个周期，但结果并未发现温度降低。先前的平均Beta晶粒尺寸；已经为该领域的未来工作提出了建议。由BE粉末生产出完全致密的氢化纳米晶TiAl压块。机械合金化的氢化粉末在850°C的HIP'ing导致均匀的微观结构，而在非氢化粉末制得的样品中可以看到先前的粉末颗粒边界。通过真空退火除去氢，得到纳米级的γ-TiAl。

著录项

  • 作者

    Qazi, Javaid Iqbal.;

  • 作者单位

    University of Idaho.;

  • 授予单位 University of Idaho.;
  • 学科 Engineering Materials Science.; Engineering Metallurgy.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 265 p.
  • 总页数 265
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;冶金工业;
  • 关键词

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