DOI: 10.5061/dryad.jm63xsjk3
title: High resolution dataset of plastic deformation at cryogenic temperatures in a nickel-based superalloy

description: A nickel-based superalloy is examined during monotonic deformation at
 cryogenic temperatures, reaching as low as liquid helium temperature. A
 detailed multimodal analysis of the microstructure and plasticity is
 conducted to discern changes in deformation mechanisms and plastic
 deformation localization under cryogenic conditions. This study employs
 high-resolution digital image correlation to identify the deformation
 mechanisms and understand their influence on plastic deformation
 localization as the temperature varies. At cryogenic temperatures, unusual
 plastic deformation localization processes are observed, attributed to the
 competing activation of a range of deformation processes. Furthermore, a
 mechanism of slip delocalization, i.e., local plastic deformation
 homogenization through closely spaced slip, is noted at these extreme
 temperatures. Ultimately, the impact of the microstructure is identified
 across the temperature range, from room to cryogenic temperatures.
description: <strong>Material:</strong> The present study
 investigated a nickel-based superalloy, Inconel 718. The Inconel 718
 material was subjected to an annealing treatment at 1050◦C for 30 minutes,
 followed by water quenching to produce a nearly random texture and a grain
 size distribution centered at 65 μm. Subsequently, a two-step
 precipitation hardening treatment was performed by subjecting the material
 to 8 hours at 720◦C, followed by 8 hours at 620◦C. This treatment resulted
 in the formation of hardening γ’ and γ” precipitates.
 <strong>Mechanical Testing:</strong> Flat
 dogbone-shaped specimens were prepared for testing with a gauge section
 measuring 1×3 mm2. The specimens were subjected to mechanical loading
 using an electromechanical 3R VHCF MEG20TT frame equipped with a custom
 setup for cryogenic testing. The specimens are exposed to either liquid
 helium or nitrogen pushed from a dewar using helium or nitrogen gas,
 respectively. The monotonic tensile tests were conducted at a quasi-static
 strain rate between 10−5 s−1 to 10−4 s−1. Several specimens were used for
 high-resolution electron microscopy based characterization and
 measurements and deformed at liquid nitrogen temperature to 0.65%, 0.83%,
 1.53% and 3.86% and at liquid helium temperature to 0.99% of plastic
 deformation. Room temperature tensile tests were conducted in a previous
 study and the data has already been made available (Stinville, J.C. et al.
 (2022). Multi-modal dataset of a polycrystalline metallic material: 3D
 microstructure and deformation fields [Dataset]. Dryad. https://doi.org/10.5061/dryad.83bk3j9sj). <strong>High-Resolution Digital Image Correlation: </strong>Before deformation, a speckle pattern consisting of 60 nm silver nanoparticles was formed on the surface of the sample. HR-DIC was performed upon completion of each step using the Heaviside DIC method. HR-DIC images were captured before loading and after unloading for subsequent analysis. The SEM images (6144 px × 4096 px) were divided into subsets of 31 × 31 pixels (700 nm × 700 nm) with an overlap of 28 pixels between each subset, i.e., step size of 3 pixels (67 nm). Scanning electron microscopy (SEM) characterization was performed using a Thermo Fisher Scientific™ (TFS) Scios Dual Beam SEM with a field emission gun (FEG). The imaging was conducted over areas with dimensions of 1076x1030 μm2, using a 9×13 grid pattern and 6x5 grid pattern with 15 % overlap between neighboring images. The imaging was performed at an accelerating voltage of 10 kV and a current of 0.80 nA. The images were acquired with a dwell time of 10 μs, with a horizontal field width of approximately 138 μm, at a working distance of 5 mm. The resulting images had a pixel resolution of 6144 px × 4096 px. Automated imaging was performed using the AutoScript software from ThermoFisher™ and a custom Python routine for automated focus/astigmatism and grid imaging before and after deformation. 
description: # High resolution dataset of plastic deformation at cryogenic temperatures
 in a nickel-based superalloy
 [https://doi.org/10.5061/dryad.jm63xsjk3](https://doi.org/10.5061/dryad.jm63xsjk3) ## Methodological Information **Material:** The present study investigated a nickel-based superalloy, Inconel 718. The Inconel 718 material was subjected to an annealing treatment at 1050◦C for 30 minutes, followed by water quenching to produce a nearly random texture and a grain size distribution centered at 65 μm. Subsequently, a two-step precipitation hardening treatment was performed by subjecting the material to 8 hours at 720◦C, followed by 8 hours at 620◦C. This treatment resulted in the formation of hardening γ’ and γ” precipitates. **Mechanical Testing:** Flat dogbone-shaped specimens were prepared for testing with a gauge section measuring 1×3 mm2. The specimens were subjected to mechanical loading using an electromechanical 3R VHCF MEG20TT frame equipped with a custom setup for cryogenic testing. The specimens are exposed to either liquid helium or nitrogen pushed from a dewar using helium or nitrogen gas, respectively. The monotonic tensile tests were conducted at a quasi-static strain rate between 10−5 s−1 to 10−4 s−1. Several specimens were used for high-resolution electron microscopy based characterization and measurements and deformed at liquid nitrogen temperature to 0.65%, 0.83%, 1.53% and 3.86% and at liquid helium temperature to 0.99% of plastic deformation. Room temperature tensile tests were conducted in a previous study and the data has already been made available (Stinville, J.C. et al. (2022). Multi-modal dataset of a polycrystalline metallic material: 3D microstructure and deformation fields [Dataset]. Dryad. [https://doi.org/10.5061/dryad.83bk3j9sj).](https://doi.org/10.5061/dryad.83bk3j9sj\).) **High-Resolution Digital Image Correlation:** Before deformation, a speckle pattern consisting of 60 nm silver nanoparticles was formed on the surface of the sample. HR-DIC was performed upon completion of each step using the Heaviside DIC method. HR-DIC images were captured before loading and after unloading for subsequent analysis. The SEM images (6144 px × 4096 px) were divided into subsets of 31 × 31 pixels (700 nm × 700 nm) with an overlap of 28 pixels between each subset, i.e., step size of 3 pixels (67 nm). Scanning electron microscopy (SEM) characterization was performed using a Thermo Fisher Scientific™ (TFS) Scios Dual Beam SEM with a field emission gun (FEG). The imaging was conducted over areas with dimensions of 1076x1030 μm2, using a 9×13 grid pattern and 6x5 grid pattern with 15 % overlap between neighboring images. The imaging was performed at an accelerating voltage of 10 kV and a current of 0.80 nA. The images were acquired with a dwell time of 10 μs, with a horizontal field width of approximately 138 μm, at a working distance of 5 mm. The resulting images had a pixel resolution of 6144 px × 4096 px. Automated imaging was performed using the AutoScript software from ThermoFisher™ and a custom Python routine for automated focus/astigmatism and grid imaging before and after deformation.  ## File Description 1. **Stress_Displacement_RT.csv** This file has been provided for reference and contains the stress and displacement data for an Inconel 718 specimen deformed at room temperature. The stress values are in MPa and the displacement values are in mm. 2. **Stress_Displacement_LN2.csv** This file contains the stress and displacement data for an Inconel 718 specimen deformed at liquid nitrogen temperature. The stress values are in MPa and the displacement values are in mm. 3. **Stress_Displacement_LHe.csv** This file contains the stress and displacement data for an Inconel 718 specimen deformed at liquid helium temperature. The stress values are in MPa and the displacement values are in mm. 4. **Inconel718_LN2_1.zip** This file contains three folders named step0, step1 and step2. These folders contain the raw SEM images captured before and after deformation for the Inconel 718 sample deformed to a plastic strain of 0.65% (step1) and 0.83% (step2) at liquid nitrogen temperature. The raw images are 8-bit tiff images. 5. **Inconel718_LN2_2.zip** This file contains two folders named step0 and step1. These folders contain the raw SEM images captured before and after deformation for the Inconel 718 sample deformed to a plastic strain of 1.53% at liquid nitrogen temperature. The raw images are 8-bit tiff images. 6. **Inconel718_LN2_3.zip** This file contains two folders named step0 and step1. These folders contain the raw SEM images captured before and after deformation for the Inconel 718 sample deformed to a plastic strain of 3.86% at liquid nitrogen temperature. The raw images are 8-bit tiff images. 7. **Inconel718_LHe_2.zip** This file contains two folders named step0 and step1. These folders contain the raw SEM images captured before and after deformation for the Inconel 718 sample deformed to a plastic strain of 0.99% at liquid helium temperature. The raw images are 8-bit tiff images. ## General Information In the stress-displacement files, the first column corresponds to displacement whereas the second column corresponds to stress. For the .zip files, for each specimen, step0 corresponds to images taken prior to deformation whereas subsequent step folders correspond to images taken after deformation. Each image is named as y_x.tif, where y corresponds to the column number and x corresponds to the row number of the image grid considered on the specimen surface. For each specimen, images having the same name in the step0 folder and subsequent step folder correspond to the same region of interest on the specimen surface. For each specimen, deformed step images can be correlated with undeformed step images to generate results using conventional or advanced digital image correlation methods.