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
February 26, 2020
Room: Theater A-10
Location: San Diego Convention Ctr
Session Chair: Khalid Hattar, Sandia National Laboratories; Nikhilesh Chawla, Arizona State University
8:30 AM Invited
Probing Mechanisms of Corrosion Damage in Aluminum Alloys by Correlative Tomography and Microscopy: Nikhilesh Chawla1; 1Arizona State University
Aluminum alloys are frequently exposed to harsh environments in service. Advances in experimental methods, analytical techniques, and computational approaches, have now enabled the development of in situ techniques that allow us to probe the behavior of materials in real-time. The study of microstructures under an external stimulus (e.g., stress, temperature, environment) as a function of time is particularly exciting. X-ray synchrotron micro and nano-tomography provides 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 metallic materials, by using a time evolved, four-dimensional (4D) virtual microstructure obtained by x-ray synchrotron tomography. Case studies on grain boundary and inclusion effects on corrosion, and stress corrosion cracking in high performance aluminum will be presented and discussed. New opportunities for x-ray microtomography, including lab-scale diffraction contrast tomography, and correlative microscopy will be highlighted.
9:10 AM Invited
Relating Corrosion Susceptibility to Microstructure via Multiscale Electron Microscopy: Josh Kacher1; Jordan Key1; Jahnavi Desai1; 1Georgia Institute of Technology
While chemical homogeneity is known to induce galvanic corrosion, the role of microstructural heterogeneities on localized corrosion susceptibility has not been rigorously established. Multiscale electron microscopy approaches, including data rich multimodal analysis and in situ testing, offer a pathway to establish a statistical and mechanistic understanding of the influence of microstructure on local corrosion behavior. In this study, the corrosion behavior of AA5xxx alloys, both sensitized and unsensitized, was investigated using electron backscatter diffraction (EBSD), automated feature detection, and in situ liquid cell transmission electron microscopy experiments (LC-TEM). EBSD coupled with automated feature detection provides statistically significant correlations between corrosion pit formation and grain size, orientation, grain boundary characteristics, and geometrically necessary dislocation density. In situ LC-TEM allows direct observations of corrosion initiation events at the nanoscale. Results will be discussed in terms of microstructural influences and the role of data-based analysis in understanding localized corrosion events.
9:50 AM
In situ Study of Room Temperature Hydride Formation in Ti6Al4V and its Effect on Damage Mechanisms: Jinwoo Kim1; C. Cem Tasan1; 1Massachusetts Institute of Technology
Hydride formation is a well-known cause for brittle fracture of Ti alloys in hydrogen environment. In this study, we investigate hydride formation in a bimodal Ti6Al4V alloy at room temperature using a novel in situ hydrogen-charging technique for scanning electron microscope and synchrotron X-ray diffraction. The combined employment of these in situ techniques enables the investigation of multi-scale effects of H in the two present phases in this alloys, which are otherwise difficult to be visualized. The real-time imaging and lattice strain analysis by the in situ techniques show that the growth of a fct-type hydride phase at phase boundaries is significantly affected by volumetric expansion of adjacent β-H solid solution phase. The results also suggest how the volumetric expansion of hydride and β-phase forms local strain in surrounding α-phase and eventually influence the damage mechanism of the alloy.
10:10 AM Break
10:30 AM
Quantifying Environmentally-assisted Cracking In-situ in Ar and s-CO2 Environments: Andrew Brittan1; Camila Toledo Torres1; Peter Beck1; Lucas Teeter1; Samuel Briggs1; Guillaume Mignot1; Sebastien Teysseyre2; Julie Tucker1; 1Oregon State University; 2Canadian Nuclear Laboratories
As energy demand increases worldwide, the need for higher efficiency forms of power generation becomes more urgent. The supercritical carbon dioxide (s-CO2) Brayton cycle has shown the potential to fill this need with a thermal efficiency which can surpass 50% for operating temperatures over 700°C. However, analysis of mechanical performance of materials in s-CO2 is required before a commercially viable s-CO2 Brayton cycle system can be distributed. Oregon State University has developed the capability to perform creep and fatigue crack growth measurements in-situ at elevated temperatures and pressures using the direct current potential drop method. In this study, crack growth analysis of 316SS is performed in air, Ar, and s-CO2 at high temperature. These three environments provide the ability to compare crack growth at high temperature under different conditions of environmental assistance: no corrosion (Ar); oxidation (air); and oxidation plus carburization (s-CO2).
10:50 AM Invited
History and Future of In-situ Transmission Electron Microscopy Corrosion Experiments: Khalid Hattar1; 1Sandia National Laboratories
The increasing complexity of in-situ TEM corrosion studies has mirrored the rapid growth in microfluidic TEM experiments. Over the last decade, Sandia has explored a range of in-situ TEM corrosion experiments starting with deterioration of high purity nanocrystalline metals in brine or acetic acid solutions through localized corrosion of low-carbon steel initiated at a triple junction of ferrite and cementite phases. These efforts continue with a recently developed set of microelectromechanical TEM devices to explore stress corrosion cracking and subsequently envisioned SCC experiments. The ability to perform these increasing complex in-situ TEM microfluidic experiments provides the ability to study initiation and interactions of various corrosion mechanisms with nanometer resolution. 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.
11:30 AM
Combinatorial Studies of Stress Corrosion Sensitivity of Alloy Films: Kewei Gao1; Youpeng Song1; 1Beijing University of Science and Technology
Corrosion product film-induced stress plays an important role in corrosion and stress corrosion cracking of metallic materials. Previous studies proved that the greater film-induced stress is, the more sensitive the stress corrosion is. In this work, the Cu-Cr alloy films with a broad compositional range were deposited onto a silicon substrate with micromachined cantilever arrays by using a magnetron co-sputtering technique. Film-induced stress formed after immersion in Mattsson's solution caused the beams to bend. The deflection of the beams was continuously measured by white light interference. The results show that the change of cantilever deflection becomes more and more obvious with the increase of Cr content, that is, stress corrosion is more sensitive. The electrochemical performance of Cu-Cr alloy films was also characterized by wire beam electrode, and the results have a good agreement. This high-throughput experimental method is also applicable to other alloy film systems.