|Presently:||Sandia National Laboratories|
|Research:||Now: Hydrogen Isotopes in Metals.|
|Education:||Ph.D., Materials Science and Engineering|
B.S., Engineering and Applied Science
California Institute of Technology
|NU refbase:||Publications by Karnesky in our database|
I am a senior materials scientist at Sandia National Laboratories and study hydrogen isotopes in metals.
Research at Northwestern
My thesis work focused on aluminum-scandium (Al-Sc) alloys. Additionally, I developed novel data analysis methods for local-electrode atom-probe (LEAP) tomography and applied them to other materials systems.
Al-RE and Al-Sc-RE
Many rare-earth elements (RE) are less expensive than Sc and create precipitates with a higher lattice parameter misfit to Al and can effectively replace Sc in Al-Sc alloys. I found that erbium is less soluble and is a faster diffuser in Al than Sc and forms precipitates with a much larger interfacial free energy. Employing transmission electron microscopy and LEAP tomography, I showed that the rare earth additions change the aging behavior of precipitates. I demonstrated, through experiment and simulation, that alloy strength at room temperature is comparable to alloys with greater amounts of costly Sc and that the alloys are more resistant to creep at higher temperatures.
Prior to my research on Al-Sc-RE, I studied Al-Sc and Al-Sc-Zr alloys reinforced with alumina (Al2O3) particles. The several nanometer Al3Sc,Zr precipitates and the sub-micron Al2O3 both strengthen these high-temperature aluminum alloys, which can be used effectively up to at least 350 °C.
Precipitates are formed after aging the alloy which is conventionally cast. Particle reinforcements are added by Dispersion Strengthened Casting (DSC) by Chesapeake Composites. Electrical conductivity measurements show that the Al2O3 does not change substantially the nucleation and growth of Al3Sc,Zr precipitates. I also measured the mechanical properties of the material--most notably its creep resistance. Both DSC-Al-Sc and DSC-Al-Sc-Zr exhibit very high threshold stresses. If the loading does not exceed these threshold stresses, the creep rate isn't experimentally measurable. I developed dislocation climb and detachment models in order to explain this behavior
Other Atom-Probe Tomography Work
I am interested in novel methods of atom-probe tomographic data analysis. I helped to develop and apply algorithms to fit precipitates as ellipsoids and to find the edge-to-edge interprecipitate distance distribution to nickel-based superalloys and Fe-Cu steel.
I am originally from Richland, WA. It was there that I first developed an interest in materials science--through blacksmithing. I earned my Bachelor of Science degree from the California Institute of Technology in 2002 in Engineering and Applied Science. I studied materials science there. I worked at the Laser Interferometer Gravitational Wave Observatory at Hanford for one summer. I then did research with Assistant Professor Ersan Üstündag's group, including work for the Spectrometer for Materials Research at Temperature and Stress at Los Alamos National Lab.
- Ph.D. Dissertation
- van Dalen, Marsha E.; Karnesky, Richard A.; Cabotaje, Joseph R.; Dunand, David C.; Seidman, David N. (2009). "Erbium and Ytterbium Solubilities and Diffusivities in Aluminum as Determined by Nanoscale Characterization of Precipitates". Acta Materialia 57 (14): 4081-4089. doi:10.1016/j.actamat.2009.05.007.
- Karnesky, Richard A.; Dunand, David C.; Seidman, David N. (2009). "Evolution of Nanoscale Precipitates in Al Microalloyed with Sc and Er". Acta Materialia 57 (14): 4022-4031. doi:10.1016/j.actamat.2009.04.034.
- Karnesky, Richard A.; van Dalen, Marsha E.; Dunand, David C.; Seidman, David N. (2006). "Effects of Substituting Rare-Earth Elements for Scandium in a Precipitation-Strengthened Al 0.08 at.% Sc Alloy". Scripta Materialia 55 (5): 437-440. doi:10.1016/j.scriptamat.2006.05.021.
- Karnesky, Richard A.; Seidman, David N.; Dunand, David C. (2006). "Creep of Al-Sc Microalloys with Rare-Earth Element Additions". Materials Science Forum 519-521: 1035-1040. doi:10.4028/www.scientific.net/MSF.519-521.1035.
- Karnesky, Richard A.; Meng, Liang; Dunand, David C. (2007). "Strengthening Mechanisms in Aluminum Containing Coherent Al3Sc Precipitates and Incoherent Al2O3 Dispersoids". Acta Materialia 55 (4): 1299-1308. doi:10.1016/j.actamat.2006.10.004.
- Karnesky, Richard A.; Sudbrack, Chantal K.; Seidman, David N. (2007). "Best-Fit Ellipsoids of Atom-Probe Tomographic Data to Study Coalescence of γ' (L12) Precipitates in Ni-Al-Cr". Scripta Materialia 57 (4): 353-356. doi:10.1016/j.scriptamat.2007.04.020.
- Karnesky, Richard A.; Isheim, Dieter; Seidman, David N. (2007). "Direct Measurement of 2-Dimensional and 3-Dimensional Interprecipitate Distance Distributions from Atom-Probe Tomographic Reconstructions". Applied Physics Letters 91 (1): 013111:1-3. doi:10.1063/1.2753097.
- Üstündag, Ersan; Karnesky, Richard A.; Daymond, Mark R.; Noyan, I. C. (2006). "Dynamical Diffraction Peak Splitting in Time-of-Flight Neutron Diffraction". Applied Physics Letters 89 (23): 233515:1-3. doi:10.1063/1.2402220.