The precipitates were therefore cha

The precipitates were therefore characterized as primary grain boundary or interior grain γ′ based on their location. Unfortunately, the etched SE images that provide clear details of the primary γ′, do not provide suitable contrast to highlight the grain boundaries. To overcome this issue, EBSD techniques were used on the lightly etched samples to determine the area fraction and size of primary γ′ at grain boundaries (from a large sample area). Because the primary γ′ was lightly etched, the precipitates produced very poor diffraction data. When the inverse pole map was combined with the image quality map and SE image, primary γ′ were differentiated from the γ grains by orientation color, size and morphology differences evident in the EBSD data. Data was collected on an FEI XL30 SEM operating at 20 kV, using a high speed Bruker camera, with a step size of 50 nm. Higher resolution, etched SE images (taken on an FEI Quanta SEM operating at 5 kV at magnifications of approximately 20,000 for secondary, and 6000 for primary) were used to determine the total primary γ′ area fraction. Photoshop image analysis software was used to analyze the SEM images. The interior primary γ′ value was determined by subtracting the grain boundary measured value (EBSD data) from the total (SE data). The resulting interior grain primary γ′ number density was combined with the measured secondary γ′ number density to provide the average secondary γ′ area fraction andprecipitate size used in the yield model.

Thin transmission electron microscope (TEM) foils and tapered atom probe tomography (APT) needles were produced at 6 mm, 50 mm, and 1 mm distances from the weld interface for use in APT and TEM analysis. The foils were milled from the sample using an FEI Nova 200 NanoLab Dual Beam (focused ion beam) FIB equipped with a Gaþ ion source and Pt gas injection system. TEM images were produced using a FEI Tecnai operating at 200 kV in both bright field and dark field modes and analyzed using Image J software [28]. Image J is a public domain Java based image analysis program that provides a processing framework for plugins and macros. Specific scripts were used to segment and measure γ′ in 10 dark field images from each of the TEM foil positions. APT samples were attached to silicon micro-tips and shaped to provide the required geometry. They were analyzed using a Cameca 3000X HR local electrode atom probe (LEAP) in LASER mode with an evaporation rate of 0.5–0.7%. The evaporation was done at a temperature of 40 K with a power of 0.3 nJ. 3D sample reconstructions and chemical compositions within the matrix and γ′ precipitates were developed using IVASs probe micro analysis (EPMA) measurements were obtained using a Cameca microprobe with line scans across the material, perpendicular to the weld interface. The total length of each line scan was 12 mm, covering 6 mm on either side of the weld line.The spacing between the measured points along the lines was 1 mm between 0 and 200 mm from the IFW interface on the Mar-M247 side and 0–350 mm from the IFW interface on the LSHR side.

Beyond these segments, the spacing between the measured points was 100 mm. Hardness measurements were obtained with a Shimadzu Dynamic Ultra-micro Hardness Tester (model DUH-211s) using a 98 mN load and 10 s hold time. At least 10 hardness measurements in the “y” direction were conducted at each “x” distance from the weld interface and averaged to provide the final value. Each of the measurements in the “y” direction were separated by at least 100 mm.

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The precipitates were therefore characterized as primary grain boundary or interior grain γ 'based on their location. Unfortunately, the etched SE images that provide clear details of the primary γ ', do not provide suitable contrast to highlight the grain boundaries. To overcome this issue, EBSD techniques were used on the lightly etched samples to determine the area fraction and size of primary γ 'at grain boundaries (from a large sample area). Because the primary γ 'was lightly etched, the precipitates produced very poor diffraction data. When the inverse pole map was combined with the image quality map and SE image, primary γ 'were differentiated from the γ grains by orientation color, size and morphology differences evident in the EBSD data. Data was collected on an FEI XL30 SEM operating at 20 kV, using a high speed Bruker camera, with a step size of 50 nm. Higher resolution, etched SE images (taken on an FEI Quanta SEM operating at 5 kV at magnifications of approximately 20,000 for secondary, and 6000 for primary) were used to determine the total primary γ 'area fraction. Photoshop image analysis software was used to analyze the SEM images. The interior primary γ 'value was determined by subtracting the grain boundary measured value (EBSD data) from the total (SE data). The resulting Interior Grain primary gamma 'Number density was combined with the measured Secondary gamma' Number density to provide the average Secondary gamma 'Area fraction Andprecipitate Size used in the yield Model. Thin Transmission Electron Microscope (TEM) foils and tapered Atom probe Tomography (. APT) needles were produced at 6 mm, 50 mm, and 1 mm distances from the weld interface for use in APT and TEM analysis. The foils were milled from the sample using an FEI Nova 200 NanoLab Dual Beam (focused ion beam) FIB equipped with a Gaþ ion source and Pt gas injection system. TEM images were produced using a FEI Tecnai operating at 200 kV in both bright field and dark field modes and analyzed using Image J software [28]. Image J is a public domain Java based image analysis program that provides a processing framework for plugins and macros. Specific scripts were used to segment and measure γ 'in 10 dark field images from each of the TEM foil positions. APT samples were attached to silicon micro-tips and shaped to provide the required geometry. They were analyzed using a Cameca 3000X HR local electrode atom probe (LEAP) in LASER mode with an evaporation rate of 0.5-0.7%. The evaporation was done at a temperature of 40 K with a power of 0.3 nJ. 3D sample reconstructions and chemical compositions within the matrix and γ 'precipitates were developed using IVASs probe micro analysis (EPMA) measurements were obtained using a Cameca microprobe with line scans across the material, perpendicular to the weld interface. The total length of each line scan was 12 mm, covering 6 mm on either side of the weld line.The spacing between the measured points along the lines was 1 mm between 0 and 200 mm from the IFW interface on the Mar-M247 side and. 0-350 mm from the interface on the IFW LSHR Side. Beyond these segments, the Spacing between the measured points was 100 mm. Hardness measurements were obtained with a Shimadzu Dynamic Ultra-micro Hardness Tester (model DUH-211s) using a 98 mN load and 10 s hold time. At least 10 hardness measurements in the "y" direction were conducted at each "x" distance from the weld interface and averaged to provide the final value. Each of the measurements in the "y" direction were separated by at least 100 mm.