Sharma Nitin Kumar, Shekhar Shashank
Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
Micron. 2018 Apr;107:28-34. doi: 10.1016/j.micron.2018.01.009. Epub 2018 Jan 31.
Misorientation angle distribution gives information about the type and fraction of grain boundaries present in a material. Since grain boundaries affect various mechanical and functional properties of the material, the distribution of grain boundary misorientation is important in order to evaluate these properties. This becomes particularly important when we want to study the microstructure in finer detail, such as understanding the average misorientation within a grain. One of the techniques increasingly used in past two decades for characterization of grain boundary misorientation is electron back scatter diffraction (EBSD). Reliable detection of very small misorientation angles using conventional EBSD system is quite challenging due to the presence of measurement error. This makes the comprehensive characterization of microstructures difficult and prone to error. In order to prevent such problems, it is important to understand the nature of measurement error and find ways to minimize it. The present work aims to elucidate the effect of measurement error on the observed misorientation angle and its statistical distribution in low misorientation angle regime. A true strain of 0.3 was imposed during cold-rolling of Cu-5%Zn alloy sample. The rolled sample was then subjected to in-situ heating from room temperature to 500 °C (∼0.58 Tm). It was found that the overall measurement error in misorientation distribution consists of random error caused by limited angular precision and systematic error which manifests primarily in the statistical distribution of low angle misorientation. In this work, we show a way to deconvolute this overall error based on the measurement technique. We further show that this systematic error is not limited to any particular measurement technique, rather related to the presence of a lower bound in the measurement.
取向差角分布给出了材料中存在的晶界类型和比例的信息。由于晶界会影响材料的各种力学性能和功能特性，因此晶界取向差的分布对于评估这些性能很重要。当我们想要更详细地研究微观结构，比如了解晶粒内部的平均取向差时，这一点就变得尤为重要。在过去二十年里，电子背散射衍射（EBSD）越来越多地被用于表征晶界取向差。由于存在测量误差，使用传统EBSD系统可靠地检测非常小的取向差角极具挑战性。这使得微观结构的全面表征变得困难且容易出错。为了防止此类问题，了解测量误差的本质并找到将其最小化的方法很重要。目前的工作旨在阐明测量误差对低取向差角区域中观察到的取向差角及其统计分布的影响。在对Cu-5%Zn合金样品进行冷轧时施加了0.3的真实应变。然后将轧制后的样品从室温原位加热到500 °C（约0.58 Tm）。研究发现，取向差分布中的总体测量误差由有限角度精度引起的随机误差和主要体现在低角度取向差统计分布中的系统误差组成。在这项工作中，我们展示了一种基于测量技术对这种总体误差进行去卷积的方法。我们进一步表明，这种系统误差并不局限于任何特定的测量技术，而是与测量中存在下限有关。
