Fatigue strain mapping via digital image correlation for Ni-based superalloys: The role of thermal activation on cube slip
Fatigue strain mapping via digital image correlation for Ni-based superalloys: The role of thermal activation on cube slip
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DOI：
10.1016/j.msea.2017.04.002
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发表时间：
2017-05
期刊：
影响因子：
6.4
通讯作者：
A. Mello;Andrea Nicolas;M. Sangid
中科院分区：
文献类型：
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作者：
A. Mello;Andrea Nicolas;M. Sangid
在低（0.7%）和高（1.0%）应变幅下，在低（300°C）、中（550°C）和高（700°C）温度下循环加载ni基高温合金的变形机理图。在每个指定的载荷和温度条件下，在高温下进行的中断疲劳实验中，通过数字图像相关（DIC）进行应变映射。DIC测量是在扫描电子显微镜下进行的，扫描电子显微镜允许对非均匀滑移事件和真空环境进行高分辨率测量，以确保DIC在高温下的散斑模式的稳定性。累积疲劳试验表明，滑移带在第一次循环中存在，并随着循环次数的增加而增强；导致高度局部应变积累。将应变映射结果与电子背散射衍射表征相结合。结合晶体取向和高分辨率应变测量来确定活动滑移面。在低温下，滑移带沿着{111}八面体平面。然而，随着温度的升高，{111}八面体和{100}立方滑移面都能适应应变。在镍基高温合金中，有序金属间γ′相内的交叉滑移激活立方滑移已经被很好地记录下来，并且通常被认为是导致异常屈服现象的机制。本文的结果代表了多晶γ-γ′ni基高温合金中尺度立方滑移系统活性的重要量化研究，这是校准多晶变形模型热激活成分的关键进展。
A deformation mechanism map for a Ni-based superalloy is presented during cyclic loading at low (300 °C), intermediate (550 °C), and high (700 °C) temperatures for low (0.7%) and high (1.0%) applied strain amplitudes. Strain mapping is performed via digital image correlation (DIC) during interrupted fatigue experiments at elevated temperatures at 1, 10, 100 and 1000 cycles, for each specified loading and temperature condition. The DIC measurements are performed in a scanning electron microscope, which allows high-resolution measurements of heterogeneous slip events and a vacuum environment to ensure stability of the speckle pattern for DIC at high temperatures. The cumulative fatigue experiments show that the slip bands are present in the first cycle and intensify with number of cycles; resulting in highly localized strain accumulation. The strain mapping results are combined with microstructure characterization via electron backscatter diffraction. The combination of crystal orientations and high-resolution strain measurements was used to determine the active slip planes. At low temperatures, slip bands follow the {111} octahedral planes. However, as temperature increases, both the {111} octahedral and {100} cubic slip planes accommodate strain. The activation of cubic slip via cross-slip within the ordered intermetallic γ’ phase has been well documented in Ni-based superalloys and is generally accepted as the mechanism responsible for the anomalous yield phenomenon. The results in this paper represent an important quantifiable study of cubic slip system activity at the mesoscale in polycrystalline γ-γ’ Ni-based superalloys, which is a key advancement to calibrate the thermal activation components of polycrystalline deformation models.