Khalid Hattar

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Dr. Khalid Hattar
Sandia National Laboratory
"Effect of friction stir welding and self-ion irradiation on dispersoid evolution in oxide dispersion strengthened steel MA956 up to 25 dpa" Elizabeth Getto, Brad Baker, B. Tobie, Samuel A. Briggs, Khalid Hattar, K. Knipling, Journal of Nuclear Materials Vol. 515 2018 407-419 Link
"Formation of tetragonal gas bubble superlattice in bulk molybdenum under helium ion implantation" Cheng Sun, David Sprouster, Khalid Hattar, Lynne Ecker, Lingfeng He, Y. Gao, Yipeng Gao, Yongfeng Zhang, Jian Gan, Scripta Materialia Vol. 149 2018 26-30 Link
We report the formation of tetragonal gas bubble superlattice in bulk molybdenum under helium ion implantation at 573 K. The transmission electron microscopy study shows that the helium bubble lattice constant measured from the in-plane d-spacing is ~4.5 nm, while it is ~3.9 nm from the out-of-plane measurement. The results of synchrotron-based small-angle x-ray scattering agree well with the transmission electron microscopy results in terms of the measurement of bubble lattice constant and bubble size. The coupling of transmission electron microscopy and synchrotron high-energy X-ray scattering provides an effective approach to study defect superlattices in irradiated materials.
"Observations of defect structure evolution in proton and Ni ion irradiated Ni-Cr binary alloys" Samuel A. Briggs, Khalid Hattar, Janne Pakarinen, Kumar Sridharan, Mitra Taheri, Christopher Barr, Mahmood Mamivand, Dane Morgan, Journal of Nuclear Materials Vol. Volume 479 2016 48-58 Link
Two binary Ni-Cr model alloys with 5 wt% Cr and 18 wt% Cr were irradiated using 2 MeV protons at 400 and 500 °C and 20 MeV Ni4+ ions at 500 °C to investigate microstructural evolution as a function of composition, irradiation temperature, and irradiating ion species. Transmission electron microscopy (TEM) was applied to study irradiation-induced void and faulted Frank loops microstructures. Irradiations at 500 °C were shown to generate decreased densities of larger defects, likely due to increased barriers to defect nucleation as compared to 400 °C irradiations. Heavy ion irradiation resulted in a larger density of smaller voids when compared to proton irradiations, indicating in-cascade clustering of point defects. Cluster dynamics simulations were in good agreement with the experimental findings, suggesting that increases in Cr content lead to an increase in interstitial binding energy, leading to higher densities of smaller dislocation loops in the Ni-18Cr alloy as compared to the Ni-5Cr alloy.
"Radiation damage in nanostructured materials" Xinghang Zhang, Khalid Hattar, Youxing Chen, Lin Shao, Jin Li, Cheng Sun, Kaiyuan Yu, Nan Li, Mitra Taheri, Haiyan Wang, Progress in Materials Science Vol. 96 2018 217-321 Link
"Effect of Friction Stir Welding on Microstructure Evolution on in situ and ex situ Self-Ion Irradiated MA956" Elizabeth Getto, Samuel A. Briggs, Khalid Hattar, Brad Baker, TMS 2018 March 11-15, (2018)