Measurement of local plastic strain during uniaxial reversed loading of nickel alloy 625
Measurement of local plastic strain during uniaxial reversed loading of nickel alloy 625
复制标题
镍合金625单轴反向加载过程中局部塑性应变的测量
DOI：
10.1016/j.matchar.2020.110561
复制
发表时间：
2020
影响因子：
4.7
通讯作者：
J. Fonseca
中科院分区：
文献类型：
--
作者：
M. Atkinson;J. Donoghue;J. Fonseca
预测多晶合金的反向加载行为具有挑战性，因为它依赖于复杂的多尺度相互作用，而这些相互作用尚未得到很好的理解和研究。采用高分辨率数字图像相关（HRDIC）技术，以亚微米空间分辨率测量了镍基高温合金反加载过程中的局部应变发展。一个特殊设计的钻机确保变形在反转过程中保持单轴，并且测量是在原位进行的，样品处于载荷下。利用电子背散射衍射（EBSD）的取向图将变形数据与潜在的晶体微观结构相关联，并使用仿射变换进行转换，以解释与测量相关的畸变。发现应变局部分布在晶体滑移带中，这些滑移带被低得多的弹性应变区分开。卸载时，在滑移带或其他地方没有测量到局部变形逆转，这意味着大部分应变逆转是弹性的，卸载时的塑性很小，分布均匀，无法用HRDIC检测到。这些结果表明，对卸载样品的HRDIC研究可以提供材料在反转过程中变形状态的代表性测量。在反转时，变形主要由前向加载过程中形成的滑移带来调节。然而，在某些晶粒中，滑移带图案随着进一步变形而改变位置并变得锋利。这表明滑移带尺度下滑移逆转的滑移程度是有限的，并且可以量化，为研究先进合金的反向加载开辟了一条新的途径。
The reverse loading behaviour of polycrystalline alloys is challenging to predict, as it depends on complex multi-scale interactions that are not well understood and difficult to study. We have used high resolution digital image correlation (HRDIC) to measure the local strain development during reversed loading of a nickel based superalloy with sub-micron spatial resolution. A specially designed rig ensured that deformation remained uni-axial during reversal, and measurements were made in-situ, with the sample under load. The deformation data was correlated with the underlying crystallographic microstructure using orientation maps from electron back-scatter diffraction (EBSD), which was transformed using an affine transformation, to account for measurement related distortion. The strain was found to be localised into crystallographic slip bands separated by regions with much lower, mostly elastic, strain. On unloading, no localised deformation reversal could be measured in slip bands or elsewhere, implying that most of the strain reversal is elastic and that any plasticity during unloading is small, evenly distributed, and could not be detected using HRDIC. These results imply that HRDIC studies on unloaded samples can provide representative measurements of the deformed state of the material during reversal. On reversal, deformation is accommodated primarily by slip on slip bands formed during forward loading. In some grains, however, the slip band patterns appear to change location and sharpen with further deformation. This suggests that slip extent of slip reversal at the scale of slip bands is limited and can be quantified, opening up a new way to study reverse loading in advanced alloys.