Seeing is Believing -- Understanding Environmental Degradation and Mechanical Response Using Advanced Characterization Techniques: An SMD Symposium in Honor of Ian M. Robertson: Environmental Degradation II: Stress Corrosion Cracking,Ccorrosion, and Liquid Metal Embrittlement
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Chemistry and Physics of Materials Committee, TMS: Corrosion and Environmental Effects Committee, TMS: Mechanical Behavior of Materials Committee, TMS: Nuclear Materials Committee
Program Organizers: Kaila Bertsch, Lawrence Livermore National Laboratory; Khalid Hattar, Sandia National Laboratories; Josh Kacher, Georgia Institute of Technology; Bai Cui, University of Nebraska-Lincoln; Benjamin Eftink, Los Alamos National Laboratory; Stephen House, University of Pittsburgh; May Martin, National Institute Of Standards And Technology; Kelly Nygren, Cornell High Energy Synchrotron Source; Blythe Clark, Sandia National Laboratories; Shuai Wang, Southern University of Science and Technology

Wednesday 8:30 AM
March 2, 2022
Room: 207C
Location: Anaheim Convention Center

Session Chair: Kaila Bertsch, Lawrence Livermore National Laboratory; Bai Cui, University of Nebraska- Lincoln; Kelly Nygren, Cornell University/CHESS; May Martin, National Institute of Standards and Technology; Shuai Wang, Southern University of Science and Technology


8:30 AM  Invited
Liquid Metal Embrittlement: Mechanisms at Small Scales: Thierry Auger1; 1CNRS
     Liquid metal embrittlement (LME) is a surface adsorption induced brittle fracture phenomenon that is still not well understood phenomenologically in spite of its technological importance and its intrinsic interest. Recent results on LME crack path investigations will be presented, mostly with LME of austenitic steels, at sub-micron resolution allowed by advanced combined FIB/TEM techniques that show that the correct inclusion of plastically induced microstructural changes are essential in the clear identification of the fracture mode of several LME cases. It can be shown that the phenomenology of LME is therefore essentially an interfacial fracture phenomenon in the case of steels, a conclusion that SEM observations alone does not allow to reach. This enables first to derive metallurgical strategies to mitigate LME with austenitic steels.Then, a modelling strategy for LME based on the ductile to brittle transition at the grain boundary is proposed as a step towards a predictive framework.

9:00 AM  Invited
On the Path to Understanding Stress Corrosion Crack Initiation of Austenitic Alloys in High Temperature Water: Gary Was1; Drew Johnson2; Wejun Kuang3; Diana Farkas4; Ian Robertson5; 1University of Michigan; 2Idaho National Laboratory; 3Xi'an Jiaotong University; 4Virginia Tech; 5University of Wisconsin
    The similarity of factors responsible for crack initiation in nickel base alloys and irradiated stainless steels suggests a common mechanism. While a general understanding of the process is emerging, there are several interesting observations that have yet to be incorporated into a complete description of the mechanism. It is now known that the local stress at sites of dislocation channel impingement at grain boundaries in irradiated stainless steel plays a critical role. In nickel-base alloys, preferential internal oxidation plays a key role. In both systems, diffusion induced grain boundary migration, the protective nature of the surface oxide over the grain boundary, and the alloy chromium content appear to be key factors affecting crack initiation., with second phases near grain boundaries and minor elements playing minor roles. This talk will focus on identification and discussion of these processes involved in crack initiation in high temperature water and a possible unifying mechanism.

9:30 AM  Invited
Understanding Basic Properties and Degradation Mechanisms of Materials Using Ion Beams: Steven Zinkle1; Ling Wang2; Yan-Ru Lin1; 1University of Tennessee; 2Oak Ridge National Laboratory
    Atomic displacement processes associated with ion beam irradiations can provide insight on numerous materials phenomena including intrinsic phase stability, fundamental point defect migration energies, and hardening mechanisms. This presentation will present illustrative examples on a wide range of materials phenomena that are accelerated by particle bombardment including ballistic dissolution and radiation enhanced coarsening of precipitates, stress-enhanced vacancy migration, 1D long range migration of defect clusters, temperature-dependent cavity formation, and hardening and softening processes in structural materials. In general, regions near surfaces or grain boundaries and near the implanted ion region should be avoided for quantitative analyses due to potential artifacts, although in some cases these artifacts can be beneficially used to provide additional insight on fundamental materials properties. Superposition of hardening contributions associated with multiple types of dislocation obstacles will also be discussed. Several examples using ion implantation or irradiation as diagnostic monitors for fundamental materials phenomena will be summarized.

10:00 AM Break

10:15 AM  Invited
Special Effects Testing and Advanced Characterization for the Development of a Multi-scale Model of Corrosion Fatigue Crack Growth that Incorporates Environmental Effects: Bryan Miller1; 1Naval Nuclear Laboratory
    Utilizing advanced characterization techniques to identify fundamental metallurgical processes that occur when materials are exposed to extreme conditions/environments is a requirement for nearly all students who work with Ian. Understanding the synergistic effects of corrosion and deformation processes at a fatigue crack tip on the bulk fatigue crack growth behavior of stainless steel alloys exposed to the high purity water environments typical of pressurized water nuclear power plants is the current focus of this former student. This presentation will focus on work utilizing a combination of special effects testing and advanced characterization techniques to identify whether a hydrogen-based mechanism is associated with corrosion fatigue crack growth in elevated temperature, high purity water. Integrating the knowledge gleaned from this work to the development of a multi-scale model of corrosion fatigue crack growth, which incorporates environmental effects, to predict fatigue crack growth rates will also be discussed.

10:45 AM  Invited
Validated Theory-guided Design of Refractory Multi-principal-element Alloys with Oxidation-resistant Coatings: Duane Johnson1; Prashant Singh1; Andrey Smirnov1; Gaoyuan Ouyang1; Jun Cui1; RanRan Su2; John Perepezko2; Matt Kramer1; 1Iowa State University Ames Laboratory; 2University of Wisconsin
    Refractory-based multiple-principal-elements alloys (MPEAs), with high-entropy alloys being a near-equiatomic subset, show great thermal stability and excellent high-temperature properties, except maybe oxidation resistance, and so some promise for replacing nickel-based superalloys as next-generation high-temperature materials. We showcase our theory-guided approach in down-selecting refractory MPEAs, and the effects of vacancies on phase selection and short-range order on strengthening. Using novel density-functional theory methods, we quantitatively predict key properties for arbitrary solid-solution alloys, e.g., structural, mechanical, stability, short-range order, and defect energies. Novel DFT-based predictions inform bulk combinatorial arc-melt synthesis and characterization, for verification and down-selection of superior mechanical properties and oxidation resistance. Then, for high-temperature applications and harsh environments, a protective, self-healing coating added to samples yield negligible mass change for (currently) 450+ hours at 1300oC. As “Seeing is Believing”, a few systems are highlighted both for theory-guided design and validation experiments.