scholarly journals Selectively Electron-Transparent Microstamping Toward Concurrent Digital Image Correlation and High-Angular Resolution Electron Backscatter Diffraction (EBSD) Analysis

2017 ◽  
Vol 23 (6) ◽  
pp. 1091-1095 ◽  
Author(s):  
Timothy J. Ruggles ◽  
Geoffrey F. Bomarito ◽  
Andrew H. Cannon ◽  
Jacob D. Hochhalter
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Angular Resolution ◽  
Electron Backscatter Diffraction ◽  
Image Correlation ◽  
Ebsd Analysis ◽  
High Angular Resolution ◽  
Resolution Electron ◽  
Electron Backscatter ◽  
Backscatter Diffraction

AbstractDigital image correlation (DIC) in a scanning electron microscope and high-angular resolution electron backscatter diffraction (HREBSD) provide valuable and complementary data concerning local deformation at the microscale. However, standard surface preparation techniques are mutually exclusive, which makes combining these techniques in situ impossible. This paper introduces a new method of applying surface patterning for DIC, namely a urethane microstamp, that provides a pattern with enough contrast for DIC at low accelerating voltages, but is virtually transparent at the higher voltages necessary for HREBSD and conventional EBSD analysis. Furthermore, microstamping is inexpensive and repeatable, and is more suitable to the analysis of patterns from complex surface geometries and larger surface areas than other patterning techniques.

scholarly journals Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

2016 ◽  
Vol 472 (2189) ◽  
pp. 20150792 ◽  
Author(s):  
Tiantian Zhang ◽  
Jun Jiang ◽  
Ben Britton ◽  
Barbara Shollock ◽  
Fionn Dunne
Keyword(s):  
Fatigue Crack ◽  
Crystal Plasticity ◽  
Electron Backscatter Diffraction ◽  
Crack Nucleation ◽  
Image Correlation ◽  
Fatigue Crack Nucleation ◽  
Resolution Electron ◽  
Electron Backscatter ◽  
Mechanistic Basis ◽  
Backscatter Diffraction

A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270–1480 MPa.

scholarly journals Deformation compatibility in a single crystalline Ni superalloy

2016 ◽  
Vol 472 (2185) ◽  
pp. 20150690 ◽  
Author(s):  
Jun Jiang ◽  
Tiantian Zhang ◽  
Fionn P. E. Dunne ◽  
T. Ben Britton
Keyword(s):  
Electron Backscatter Diffraction ◽  
Deformation Gradient ◽  
Advanced Characterization ◽  
Image Correlation ◽  
Polycrystalline Materials ◽  
High Angular Resolution ◽  
Resolution Electron ◽  
Backscatter Diffraction ◽  
Deformation Gradients

Deformation in materials is often complex and requires rigorous understanding to predict engineering component lifetime. Experimental understanding of deformation requires utilization of advanced characterization techniques, such as high spatial resolution digital image correlation (HR-DIC) and high angular resolution electron backscatter diffraction (HR-EBSD), combined with clear interpretation of their results to understand how a material has deformed. In this study, we use HR-DIC and HR-EBSD to explore the mechanical behaviour of a single-crystal nickel alloy and to highlight opportunities to understand the complete deformations state in materials. Coupling of HR-DIC and HR-EBSD enables us to precisely focus on the extent which we can access the deformation gradient, F , in its entirety and uncouple contributions from elastic deformation gradients, slip and rigid body rotations. Our results show a clear demonstration of the capabilities of these techniques, found within our experimental toolbox, to underpin fundamental mechanistic studies of deformation in polycrystalline materials and the role of microstructure.

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