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Shear localization and its related microstructural evolution in the ultrafine grained titanium processed by multi-axial compression

机译:多轴压缩钛超细晶粒中的剪切局部化及其相关的组织演变

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摘要

Ultrafine grained titanium has unique mechanical properties and attracts tremendous interest due to its scientific and technological application. Shear localization is frequently denoted as adiabatic shear band, and is one of the most important deformation and failure mechanisms for it used at high rate deformation. Hat shaped specimens are used to induce the formation of an adiabatic shear band under controlled dynamic conditions. Unstable shear deformation of the alloy emerges after the true flow stress reaches about 750 MPa, the first vibration peak during the split Hopkinson pressure bar testing, and the whole deformation process lasts about 50 μs. The microstructure and microtextures in the shear band with width about 16.7 μm in ultrafine grained titanium processed by multi-axial compression are investigated by means of optical microscopy, scanning electron microscopy/electron back-scattered diffraction, and transmission electron microscopy. The results show that the grains in the boundary of the shear band are highly elongated along the shear direction, and the core of the shear band consists of a number of scattered recrystallized equiaxed grains with 50-80 nm in diameters and coalesced grains with 100-150 nm in diameters. Some new microtextures (20°, 4°, 0°), (81°, 0°, 0°), and (55°, 0°, 30°) with recrystallized characteristics are generated in the shear band. The grain boundaries in the core of an adiabatic shear band are high-angle boundaries and geometrical necessary boundaries created with aims of accommodating the imposed shear strain. Calculations of temperature rise suggest that the maximum temperature in the shear band is about 870 K being sufficient for the recrystallization. Finally, the mechanisms of formation of an adiabatic shear band in the ultrafine grained titanium processed by multi-axial compression and its microstructural evolution are proposed.
机译:超细晶粒钛具有独特的机械性能,并且由于其科学和技术应用而引起了极大的兴趣。剪切局部化通常被称为绝热剪切带,并且是在高速变形下使用的最重要的变形和破坏机制之一。帽形样品用于在受控动态条件下诱导绝热剪切带的形成。在真流应力达到约750 MPa之后,合金出现了不稳定的剪切变形,这是在霍普金森分体式压力棒测试期间的第一个振动峰,整个变形过程持续约50μs。通过光学显微镜,扫描电子显微镜/电子背散射衍射和透射电子显微镜研究了经多轴压缩处理的超细晶粒钛剪切带中约16.7μm宽的组织和显微组织。结果表明,剪切带边界处的晶粒沿剪切方向高度伸长,剪切带的核心由许多直径为50-80 nm的分散重结晶等轴晶粒和100-100 nm的聚结晶粒组成直径为150 nm。在剪切带中产生了一些具有重结晶特性的新的微观纹理(20°,4°,0°),(81°,0°,0°)和(55°,0°,30°)。绝热剪切带的核心中的晶界是大角度的边界和几何上必要的边界,其目的是为了适应所施加的剪切应变。温升的计算表明,剪切带中的最高温度约为870 K,足以进行重结晶。最后,提出了多轴压缩钛超细晶粒绝热剪切带的形成机理及其微观组织演变。

著录项

  • 来源
    《Materials Science and Engineering》 |2014年第26期|227-235|共9页
  • 作者单位

    School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan, People's Republic of China,Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093, United States,Department of Nanoengineering, University of California, San Diego, CA 92093, United States,Key lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083, Hunan, People's Republic of China,University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, United States;

    School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan, People's Republic of China;

    School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan, People's Republic of China;

    School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan, People's Republic of China;

    School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan, People's Republic of China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Shear bands; Recrystallization; Electron microscopy; Titanium; Ultrafine grain;

    机译:剪切带;重结晶;电子显微镜;钛;超细颗粒;

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