Environmental Degradation of Multiple Principal Component Materials: Aqueous Corrosion and Embrittlement
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee, TMS: Nuclear Materials Committee
Program Organizers: Wenjun Cai, Virginia Polytechnic Institute and State University; ShinYoung Kang, Lawrence Livermore National Laboratory; XiaoXiang Yu, Novelis Global Research Center; Vilupanur Ravi, California State Polytechnic University Pomona; Christopher Weinberger, Colorado State University; Elizabeth Opila, University of Virginia; Bai Cui, University of Nebraska-Lincoln; Mark Weaver, University of Alabama; Bronislava Gorr, Karlsruhe Institute of Technology (KIT); Srujan Rokkam, Advanced Cooling Technologies, Inc.

Wednesday 2:00 PM
March 2, 2022
Room: 201C
Location: Anaheim Convention Center

Session Chair: Wenjun Cai, Virginia Tech; Bai Cui, University of Nebraska-Lincoln

2:00 PM  
The Tribocorrosion Behaviors of Al0.1CrCoFeNi Multi-principal Element Alloys in Different pH Conditions: Jia Chen1; Wenbo Wang1; Wenjun Cai1; 1Virginia Polytechnic Institute and State University
    Multi-principal element alloys (MPEAs) have grained increasing interests lately due to their exceptional mechanical, tribological and corrosion properties. The combination of these properties makes them ideal candidates for various applications under extreme conditions where surface stress and corrosive environments coexist. In the present study, the effects of pH on the tribocorrosion behavior of Al0.1CrCoFeNi MPEA was studied in simulated seawater under room temperature. The microstructure of as received and tribocorroded samples were characterized by scanning electron microscopy and x-ray diffraction. The element distribution and chemical state in worn and unworn areas were studied using energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. The cross-sectional worn area was characterized by transmission electron microscopy. It was shown that this MPEA has the lowest corrosion resistance in alkaline solution, and the material loss increased with increasing pH, which is mainly dependent on the pH-dependent corrosion behavior of the alloy.

2:20 PM  
Localized Corrosion Resistance of Ni-Cr-Co-Fe-Mo MPE Alloys in Aqueous and Methanolic Environments: Angeire Huggins Gonzalez1; Narasi Sridhar2; Ramgopal Thodla1; 1DNV; 2MC Consult LLC
    The localized corrosion resistance of three Ni-Cr-Co-Fe-Mo High Entropy Alloys (HEA’s) with Pitting Resistance Equivalence Numbers (PREN) ranging from 42 to 55 were evaluated in LiCl environments in water and methanol as solvents. Three were compared to a conventional Ni-base alloy (alloy 625) with similar PREN. The literature data on the localized corrosion resistance of a commercially available Multi-Principal Element Alloy (MPEA), MP-35N (UNS R30035), is also compared. The localized corrosion resistance of the MPEA's trended with PREN along with the conventional alloys. The localized corrosion was more severe in methanolic solutions than in aqueous solutions. The localized corrosion behavior of the MPEA's are discussed in terms of the alloying effect on the electrochemical response and local chemistry.

2:40 PM  
Equivalent Hydrogen Fugacity during Electrochemical Charging of Nickel Single Crystal: Comparison with Gaseous Hydrogen Charging: Clara Juillet1; Jiaqi Li1; Caroline Traisnel1; Marie Landeiro Dos Reis1; Jamaa Bouhattate1; Abdelali Oudriss1; Laurent Briottet2; Xavier Feaugas1; 1Laboratoire des Sciences de l’Ingénieur pour l’Environnement (LaSIE); 2Univ Grenoble Alpes, CEA, LITEN, DTCH, LCA
    The hydrogen reactions of adsorption, absorption, diffusion and trapping into a metallic structure are susceptible to be enable during the application of a cathodic potential, which can lead to the materials embrittlement. These phenomena are complex and can be produced in metals by thermal or electrochemical charging. This study aimed at formalizing the link between the conditions of cathodic charging (overpotential, hydrogen flux, surface coverage) and the equivalent pressure of dihydrogen for nickel (100) single crystal by using a thermodynamic framework. The hydrogen reactions at the nickel surface in alkaline solution were dominated by the volmer-heyrovsky mechanisms at room temperature. The fugacity-real gas pressure equivalence had been established for a fugacity less than 400 atm, an overpotential between -1.2 V and -1 V and a hydrogen concentration less than 7 wt.ppm with a thermodynamic approach. The equivalence conversion model thus established will be challenged by gaseous hydrogen charging.

3:00 PM  Invited
Exploring Hydrogen-induced Martensitic Transformation and Twinning Effects Metastable Fe-Mn-Co-Cr High Entropy Alloys : C. Tasan1; Maria Ronchi1; Haoxue Yan1; 1Massachusetts Institute of Technology
    Alloys undergoing ε-martensite transformation may exhibit some resistance to hydrogen embrittlement. To better understand hydrogen effects in these alloys, we investigate the hydrogen-induced microstructural transformations in a metastable Fe45Mn35Co10Cr10 alloy. To this end, we electrochemically charge unstrained samples, quantify the hydrogen evolution by thermal desorption spectroscopy, and observe microstructural transformations by scanning electron microscopy techniques. Through these analyses, we find that the hydrogen-induced ε-martensite formation is dependent on the crystallographic orientation of the austenite grains, and takes place preferentially along Σ3 boundaries. Further charging of hydrogen induces extension twinning within the martensite. In this talk, these results will be presented as well as a new micro-mechanical approach to more efficiently explore this hydrogen effects in this alloy system.