Dr Yongfeng Zhang is currently an assistant professor in the Engineering Physics Department at University of Wisconsin-Madison. His research interest lies in materials aging and degradation in extreme conditions such as radiation, high temperature, stress and corrosive media using microstructure-based modeling. In such harsh environments, materials are subject to significant property degradations induced by a variety of mechanisms, which limit their performance. By tracking microstructure evolution and constructing structure-property correlations, the objective of Dr. Zhang's research is to uncover the degradation mechanisms in materials under extreme conditions. The research outcome will help predict the degradation rates and guide the development of novel materials for applications in extreme conditions.
Dr. Zhang obtained his PhD degree in 2009 from Rensselaer Polytechnical Institute. After that he joined Idaho National Laboratory, INL. Prior to join University of Wisconsin, He is a senior Staff Scientist at INL and leads the Computational Microstructure Science Group in the Fuel Modeling and Simulation Department.
|"Calculation of the displacement energy of alph and gamma uranium" Yongfeng Zhang, Maria Okuniewski, Chaitanya Deo, Journal of Nuclear Materials Vol. 508 2018 181--194 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,
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.
"Thermal stability of helium bubble superlattice in Mo under TEM in-situ heating"
Jian Gan, Cheng Sun, Lingfeng He, Yongfeng Zhang, Chao Jiang, Yipeng Gao,
Journal of Nuclear Materials
Although the temperature window of helium ion irradiation for gas bubble superlattice (GBS) formation was found to be in the range of approximately 0.15–0.35 melting point in literature, the thermal stability of He GBS has not been fully investigated. This work reports the experiment using an in-situ heating holder in a transmission electron microscope (TEM). A 3.0 mm TEM disc sample of Mo (99.95% pure) was irradiated with 40 keV He ions at 300 °C to a fluence of 1.0E+17 ions/cm2, corresponding to a peak He concentration of approximately 10 at.%, in order to introduce He GBS. In-situ heating was conducted with a ramp rate of ∼25 °C/min, hold time of ∼30 min, and temperature step of ∼100 °C up to 850 °C (0.39Tm homologous temperature). The result shows good thermal stability of He GBS in Mo with no noticeable change on GBS lattice constant and ordering. The implication of this unique and stable ordered microstructure on mechanistic understanding of GBS and its advanced application are discussed.