Calvin Parkin

Profile Information
Dr. Calvin Parkin
Sandia National Laboratories
Postdoctoral Appointee
Sandia National Laboratories, University of Wisconsin- Madison
Complex Concentrated Alloys (CCA), Electron Microscopy, High Entropy Alloy (HEA), In Situ Ion Irradiation, Ion-Irradiation, Nuclear Materials, Nuclear Structural Materials, Radiation Damage, Void Swelling
"In situ microstructural evolution in face-centered and body-centered cubic complex concentrated solid-solution alloys under heavy ion irradiation" Michael Moorehead, Calvin Parkin, Mohamed Elbakhshwan, Jing Hu, Wei-Ying Chen, Meimei Li, Lingfeng He, Kumar Sridharan, Adrien Couet, Acta Materialia Vol. 198 2020 85-99 Link
This study characterizes the microstructural evolution of single-phase complex concentrated solid- solution alloy (CSA) compositions under heavy ion irradiation with the goal of evaluating mecha- nisms for CSA radiation tolerance in advanced fission systems. Three such alloys, Cr 18 Fe 27 Mn 27 Ni 28 , Cr 15 Fe 35 Mn 15 Ni 35 , and equimolar NbTaTiV, along with reference materials (pure Ni and E90 for the Cr- FeMnNi family and pure V for NbTaTiV) were irradiated at 50 K and 773 K with 1 MeV Kr ++ ions to vari- ous levels of displacements per atom (dpa) using in-situ transmission electron microscopy. Cryogenic irra- diation resulted in small defect clusters and faulted dislocation loops as large as 12 nm in face-centered cubic (FCC) CSAs. With thermal diffusion suppressed at cryogenic temperatures, defect densities were lower in all CSAs than in their less compositionally complex reference materials indicating that point defect production is reduced during the displacement cascade stage. High temperature irradiation of the two FCC CSA resulted in the formation of interstitial dislocation loops which by 2 dpa grew to an average size of 27 nm in Cr 18 Fe 27 Mn 27 Ni 28 and 10 nm in Cr 15 Fe 35 Mn 15 Ni 35 . This difference in loop growth kinet- ics was attributed to the difference in Mn-content due to its effect on the nucleation rate by increasing vacancy mobility or reducing the stacking-fault energy.#171118
"Phase stability, mechanical properties, and ion irradiation effects in face-centered cubic CrFeMnNi compositionally complex solid-solution alloys at high temperatures" Calvin Parkin, Journal of Nuclear Materials Vol. 565 2022 Link
Two CrFeMnNi face-centered cubic complex concentrated solid-solution alloys (CSA) have been evaluated for phase stability, mechanical properties, and radiation damage effects from heavy ions. Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35 were predicted by thermodynamic calculations to phase separate and maintain a single phase at 700 °C, respectively. Aging experiments at this temperature confirmed varying degrees of precipitation of a body-centered cubic phase in both Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35. The alloys showed promising strength in tensile deformation at room temperature, with yield strengths of 155 MPa and 151 MPa for Cr18Fe27Mn27Ni28 and Cr15Fe35Mn15Ni35, respectively. At 500 °C, the yield strength of Cr18Fe27Mn27Ni28 fell to 93 MPa, and to 100 MPa in Cr15Fe35Mn15Ni35. Unlike Cr18Fe27Mn27Ni28, Cr15Fe35Mn15Ni35 gained some ductility at 500 °C compared to room temperature. The two CSAs were irradiated to 75 dpa at 500 °C in the plateau region of the displacement curve using 3.7 MeV Ni2+ ions, alongside model alloy 709 as a reference. Irradiation results produced similar densities and sizes of dislocations loops in the two CSAs compared to the reference. However, while large voids form in the plateau region of Cr18Fe27Mn27Ni28, small voids form just beyond the displacement peak of Cr15Fe35Mn15Ni35. Atom probe tomography and energy dispersive X-ray spectroscopy-equipped scanning transmission electron microscopes were used to characterize the alloys for changes in chemical distribution.
"Heavy Ion Irradiation of FCC and BCC High Entropy Alloys for Advanced Nuclear Reactor Applications " Calvin Parkin, Materials in Nuclear Energy Systems October 6-10, (2019) Link
"In situ and ex situ heavy ion irradiation of FCC high-entropy alloys at cryogenic and high temperatures" Calvin Parkin, NuMat 2020 January 26-29, (2021)
"In Situ heavy ion irradiation of FCC and BCC high-entropy alloys at cryogenic and high temperatures" Calvin Parkin, TMS 2020 February 23-27, (2020)
"Investigation of High-Entropy Alloys Compositions for Radiation Damage Applications" Calvin Parkin, Michael Moorehead, Zefeng Yu, Kumar Sridharan, Adrien Couet, ANS Annual Meeting 2018 June 18-22, (2018)
"Ion irradiation effects in face-centered cubic complex concentrated solid solution alloys at high temperature" Calvin Parkin, ANS Winter Meeting 2020 November 16-19, (2020)
"Microstructural Characterization of High-entropy Alloy Ion Irradiated at Cryogenic Temperatures" Michael Moorehead, Calvin Parkin, Lingfeng He, Jing Hu, Meimei Li, Adrien Couet, Kumar Sridharan, TMS 2019 March 10-14, (2019)