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

Tuesday 8:00 AM
March 1, 2022
Room: 201D
Location: Anaheim Convention Center

Session Chair: Yongfeng Lu, University of Nebraska-Lincoln; Khalid Hattar, Sandia National Laboratories

8:00 AM  Invited
NOW ON-DEMAND ONLY - A Portable Solution to Corrosion Remediation of Sea Ships to Desensitize Severely Sensitized Aluminum Alloys Using Lasers: Yongfeng Lu1; Leimin Deng1; Chenfei Zhang1; Shiding Sun1; Bai Cui1; 1University of Nebraska, Lincoln
    The 5xxx series aluminum (Al) alloy has been widely used in marine environments such as ships due to its lightweight and mechanical strength. However, it has suffered from sensitization and subsequent intergranular/stress corrosion cracking when exposed to elevated temperatures and sea water. In corrosion remediation is usually carried out by sending ships to shipyards for regular maintenance which is time consuming and costly. In this study, a portable laser system was developed to achieve laser surface desensitization (LSD) of severely sensitized 5456 Al alloys. The LSD system is portable and can be used onboard ships during operation which can significantly save time and costs. The technique could realize rapid desensitization selectively on localized surface regions and within controllable depths. A degree of sensitization (DoS) of 1.7 mg/cm2, which was even lower than the original material, was achieved from severely sensitized 5456 Al alloys (a DoS of over 46.8 mg/cm2). Moreover, LSD not only reversed the sensitization with no loss of mechanical properties but it also significantly enhanced the future sensitization resistance of Al alloys at the same time.

8:35 AM  
Effect of Grain Boundary Character on Chloride-induced Transgranular Stress Corrosion Cracking Propagation in an Austenitic Stainless Steel: Haozheng Qu1; Eric Schindelholz2; Rebecca Schaller3; Jason Taylor3; Timothy Montoya3; Nianju Gu1; Nathaniel Pettifor4; Janelle Wharry1; 1Purdue University; 2Ohio State University; 3Sandia National Laboratories; 4Ivy Tech Community College
     The objective of this presentation is to understand the effects of local stress and grain boundary (GB) type on chloride-induced stress corrosion cracking (CISCC) growth in austenitic stainless steel (AuSS). CISCC likely occurs transgranularly (TGSCC), and thus propagates through localized slip and dislocation pile-up at grain boundaries in AuSS. However, its propagation criteria are not well known. In this study, 304L SS specimens are loaded in tension in four-point bend fixtures and corroded in boiling magnesium chloride. The GB types and characters along the crack paths are characterized using scanning electron microscopy with electron backscatter diffraction (EBSD). Local stresses at specific GB positions are simulated by finite element analysis to inform the effect of stress on cracking behaviors at different GB types. These results will be discussed in the context of previously proposed TGSCC propagation criteria. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2021-7896A.

8:55 AM  Invited
Recent Developments in Coupled In-situ Transmission Electron Microscopy to Better Understand Materials Degradation: Khalid Hattar1; Katherine Jungjohann1; 1Sandia National Laboratories
    Environmentally assisted cracking and failure is fundamentally a complex process involving multiple stressors that initiates at the atomistic scale. Although the theory and modeling effort has incorporated a multi-scale approach, this has largely been limited in the experimental effort due to the difficulty of observing sample with nanometer resolution during exposure to controlled coupled environments. This presentation will highlight recent developments at Sandia National Laboratories (SNL) to advance the capabilities to study coupled extreme environments via in-situ Transmission Electron Microscopy (TEM). This will include efforts to explore in-situ TEM ion irradiation, thermal, gas, mechanical, and environmental exposure in various combinations in a range of complex materials systems. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

9:30 AM  
Relating Localized Corrosion Rates to Microstructure in Pure Al Exposed to Salt Water Environments: Bruno Geoly1; Frank Yu1; Devon Phelps1; Joseph Stover1; Michael Melia2; Philip Noell2; Josh Kacher1; 1Georgia Institute of Technology; 2Sandia National Labs
    Pitting corrosion is a form of localized corrosion that, while small in terms of volume corroded, can have an outsized influence on degradation and failure of metals and alloys. Our research focuses on understanding the rate at which corrosive pits grow over time as a function of microstructure. Specifically, we examine the relationship between microstructure and pitting corrosion rates in pure Al exposed to salt water environments by combining in situ optical microscopy corrosion experiments with electron backscatter diffraction (EBSD) analysis. From the EBSD data, we calculate the crystallographic orientation, nearby grain boundary characteristics, and the local geometrically necessary dislocation density and compare these factors to corrosion pit morphology and growth rates. This work is supported by Sandia National Laboratories (SNL). SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

9:50 AM Break

10:10 AM  
In-situ SEM Investigation of Chemo-mechanical Effects on Cutting-induced Mixed-mode II-III fracture of Martensitic Stainless Steel: Gianluca Roscioli1; Cemal Tasan1; 1Massachusetts Institute of Technology
    Sharp edges are honed from carbide-rich martensitic stainless steel and applied coatings to achieve high hardness and wear resistance. Yet they fail due to the combined chemo-mechanical actions of the environment and the mixed mode II-III stress during cutting. To investigate this process, we exposed sharp edges to increasing corrosion severity and carried out in-situ electron microscopy cutting experiments with two micro-mechanical testing setups. At low corrosion levels, surface byproducts are removed during cutting, and cracks propagate at an angle with respect to the sharp edge to form a chip. As corrosion severity increases, a percolated void structure develops and cracks propagate perpendicularly to the sharp edge, with portions of the material bending out-of-plane. Although increasing corrosion severity increases the cutting force, our numerical investigation reveals that the formation of the percolated porous structure, which increases substructural heterogeneity in the material, is responsible for the change in failure mechanism.