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Full-Text Articles in Engineering
Influence Of Grain Boundary Character On Creep Void Formation In Alloy 617, Thomas Lillo, James Cole, Megan Frary, Scott Schlegel
Influence Of Grain Boundary Character On Creep Void Formation In Alloy 617, Thomas Lillo, James Cole, Megan Frary, Scott Schlegel
Materials Science and Engineering Faculty Publications and Presentations
Alloy 617, a high temperature creep-resistant, nickel-based alloy, is being considered for the primary heat exchanger for the Next Generation Nuclear Plant (NGNP) which will operate at temperatures exceeding 760oC. Orientation imaging microscopy (OIM) is used to characterize the grain boundaries in the vicinity of creep voids that develop during high temperature creep tests (800-1000oC at creep stresses ranging from 20-85 MPa) terminated at creep strains ranging from 5-40%. Observations using optical microscopy indicate creep rate does not significantly influence the creep void fraction at a given creep strain. Preliminary analysis of the OIM data indicates …
Precipitate Redistribution During Creep Of Alloy 617, Scott Schlegel, Sharla Hopkins, E. Young, James Cole, Thomas Lillo, Megan Frary
Precipitate Redistribution During Creep Of Alloy 617, Scott Schlegel, Sharla Hopkins, E. Young, James Cole, Thomas Lillo, Megan Frary
Materials Science and Engineering Faculty Publications and Presentations
Nickel-based superalloys are being considered for applications within advanced nuclear power generation systems due to their high temperature strength and corrosion resistance. Alloy 617, a candidate for use in heat exchangers, derives its strength from both solid solution strengthening and the precipitation of carbide particles. However, during creep, carbides that are supposed to retard grain boundary motion are found to dissolve and re-precipitate on boundaries in tension. To quantify the redistribution, we have used electron backscatter diffraction and energy dispersive spectroscopy to analyze the microstructure of 617 after creep testing at 900 and 1000°C. The data were analyzed with respect …
On The Thermal Activation Of Negative Bias Temperature Instability, Richard G. Southwick Iii, William B. Knowlton, Ben Kaczer, Tibor Grasser
On The Thermal Activation Of Negative Bias Temperature Instability, Richard G. Southwick Iii, William B. Knowlton, Ben Kaczer, Tibor Grasser
Materials Science and Engineering Faculty Publications and Presentations
The temperature dependence of negative bias temperature instability (NBTI) is investigated on 2.0nm SiO2 devices from temperatures ranging from 300K down to 6K with a measurement window of ~12ms to 100s. Results indicate that classic NBTI degradation is observed down to ~200K and rarely observed at temperatures below 140K in the experimental window. Since experimental results show the charge trapping component contributing to NBTI is thermally activated, the results cannot be explained with the conventionally employed elastic tunneling theory. A new mechanism is observed at temperatures below 200K where device performance during stress conditions improves rather than degrades with …
Effect Of Grain Boundary Engineering On Microstructural Stability During Annealing, Scott M. Schlegel, Sharla Hopkins, Megan Frary
Effect Of Grain Boundary Engineering On Microstructural Stability During Annealing, Scott M. Schlegel, Sharla Hopkins, Megan Frary
Materials Science and Engineering Faculty Publications and Presentations
Grain boundary engineering, which increases the special boundary fraction, may improve microstructural stability during annealing. Different processing routes are undertaken to establish the effectiveness of each and to better understand which microstructural features determine the resulting stability. We find that multiple cycles of grain boundary engineering result in a material that resists abnormal grain growth better than other processing routes despite similarities in special boundary fraction, grain size, and general boundary connectivity among as-processed materials.