CEEM Seminar Series | Donald Brown | Los Alamos National Laboratory
Formation and Recovery of Dislocations Under Deformation and/or Irradiation of Elemental Tantalum, a Step Toward Understanding Complex BCC Alloys
Microstructure-aware models are necessary to predict mechanical properties of materials in environmental conditions which are not easily reproduced in the laboratory, e.g. nuclear reactor environments. Dislocations, whether formed through deformation or irradiation, play a controlling role in the mechanical properties of metals by increasing the flow strength and decreasing the strain to failure. Thus, it is important to develop physics-based models of the formation and recovery of dislocations under these distinct conditions. Elemental tantalum provides a relatively simple BCC system in which to develop a microstructural understanding of deformation and recovery processes which can then be applied to a much more complicated and more relevant BCC steel alloys. In-situ neutron diffraction experiments have been completed during deformation and recovery of both virgin and irradiated tantalum to monitor the evolution of the internal stress (at multiple length scales), texture and dislocation density. Attention will be paid, in particular, to the kinetics of the recovery of dislocations formed through deformation and through irradiation. Unsurprisingly, line dislocation formed by deformation responds differently than loop dislocations formed by irradiation during recovery. The results will be used to develop both polycrystalline plasticity models and Discrete Dislocation Dynamics (DDD) models of these processes.
Dr Don Brown
Dr Don Brown received his PhD in Physics from the Penn State University in 1998 focusing on using x-ray and neutron scattering techniques to characterize materials confined to nano-voids. After 20+ years at LANL, he is a recognized international leader in the field of neutron and x-ray diffraction studies of engineering materials and has pioneered studies of in-situ scattering work. In particular, he has specialized in using diffraction centric measurements in unique and relevant environments to develop and/or validate polycrystalline plasticity models of deformation. His work has focused on the study of nuclear weapons and energy materials, but included components of aerospace, automotive, and functional materials as well. Most recently, his research has included in-situ processing and performance of additively manufactured materials.