Environmentally Assisted Cracking: Theory and Practice: Innovative Techniques in Corrosion Research
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Bai Cui, University of Nebraska Lincoln; Raul Rebak, GE Global Research; Srujan Rokkam, Advanced Cooling Technologies, Inc.; Jenifer Locke, Ohio State University

Wednesday 8:30 AM
March 17, 2021
Room: RM 18
Location: TMS2021 Virtual

Session Chair: Khalid Hattar, Sandia National Lab; Michele Manuel, University of Florida


8:30 AM  Invited
Deconvoluting Mechanism in Complex Environments via In-situ Electron Microscopy: Khalid Hattar1; 1Sandia National Laboratories
    Understanding deformation, fracture, and failure of materials in complex and extreme environments is difficult to predict due to the overlapping and potentially deleterious mechanisms that might be active. This presentation will highlight recent advancements of in-situ scanning and transmission electron microscopy capabilities at Sandia National Laboratories to provide a wide combination of extreme environments. These capabilities permit nanoscale structural evolution during a range of environments including very high temperature, high cycle fatigue, displacement damage, corrosion, and combinations thereof. In contrast to the real-world extreme environments, these studies permit the ability to deconvolute the factors greatest impacting the underlying deleterious mechanisms. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

9:10 AM  Invited
Elucidation of Corrosion Mechanisms in Light Alloys by In situ X-ray Micro and Nanotomography: Nikhilesh Chawla1; 1Purdue University
    Light alloys are frequently exposed to harsh environments in service. X-ray synchrotron micro and nanotomography provide a wonderful means of characterization damage in materials non-destructively. In this talk, I will describe experiments and simulations that address the critical link between microstructure and corrosion behavior of aluminum and magnesium alloys, by using a three-dimensional (3D) virtual microstructure obtained by x-ray synchrotron tomography. In particular, precipitate location, size, and composition play a pivotal role in determining the initiation and propagation of corrosion damage light alloys. Four-dimensional (4D) in situ experiments conducted on different aging conditions yielded extremely interesting insights into the complex interplay between precipitates, grain boundaries, and inclusions. The correlative microscopy approach used here has yielded a multi-faceted understanding of the corrosion initiation and progression in these alloys at the nanoscale, which will be discussed.

9:50 AM  Invited
Controlling the Corrosion Behavior of Bioresorbable Magnesium Implants: Michele Manuel1; 1University of Florida
    Biodegradable magnesium alloys combine the advantages of traditional metallic implants and biodegradable polymers, being non-toxic and having high strength, low density, and a stiffness ideal for bone fracture fixation. Recently, a series of magnesium-based alloys that possess advantageous characteristics over other bioresorbable alloys, such as slower degradation rates and minimal toxicity were developed with a stainless, self-passivating surface layer to control the corrosion behavior. These alloys utilized elemental additions that produced low formation enthalpy oxides as a protective layer. Models and experimental validation illustrate the feasibility of this approach to develop alloys with corrosion resistance as well as other properties of interest.

10:30 AM  Invited
Understanding General Grain Boundaries: The Weak Link for Mechanical and Chemical Degradation: Jian Luo1; 1University of California, San Diego
    This talk reviews several studies focusing on general GBs. A series of our earlier studies have developed the GB counterparts to the bulk phase diagrams. Here, a grand challenge is that general GBs has five macroscopic (crystallographic) degrees of freedom (DOFs). A recent collaborative study uses genetic algorithm-guided deep learning to predict GB properties in a 7D space (5 macroscopic DOFs plus temperature and composition) [Materials Today 2020]. Furthermore, several studies investigate general GBs randomly selected from polycrystals, including two classical GB embrittlement systems: Bi [Science 2011 and 2017] vs. S [Nature Comm. 2018] doped Ni. A more complex GB superstructure with highly asymmetric segregation and interfacial reconstruction is discovered in Ti-doped WC-Co [Materials Horizons 2020]. Here, thermodynamic models, DFT calculations, atomistic simulations, machine learning, and advanced microscopy are often combined to understand the complex general GBs. Liquid metal embrittlement and corrosion will be also discussed as examples.

11:10 AM  
Classifying Liquid-solid Metal Interactions: Separation of the Multiple Mechanisms of Liquid Metal Embrittlement: Justin Norkett1; Cameron Frampton1; Victoria Miller1; 1University of Florida
    The most often considered interaction between a liquid metal and solid metal is grain boundary wetting leading to catastrophic degradation of the solid's mechanical properties, usually termed liquid metal embrittlement. However, there are numerous other liquid-solid interactions to consider, including embrittlement of single crystals, variable grain boundary penetration kinetics, and liquid-metal-mediated recrystallization. This study utilizes advanced electron microscopy techniques including electron backscatter diffraction to examine the mechanisms underlying these poorly studied phenomena. This is paired with a machine learning model to test the hypothesis that the umbrella term "liquid metal embrittlement" is actually composed of multiple separable mechanisms.