Hydrogen Embrittlement-Resistant High-Entropy Alloys with High Strength and Ductility
Shinyoung Kang | 20-LW-015
Hydrogen embrittlement (HE) of metals and alloys is a centuries-old problem that affects the mechanical stability of bridges, nuclear waste storage containers, and many other infrastructure materials. In 2017, high-entropy alloys, in which multiple metal elements are mixed in equiatomic proportions, were first proposed to dramatically slow the HE and expand lifetime of alloys by several decades. However, to design better HE-resistant alloys, deeper understanding of the intrinsic properties of high-entropy alloys and their underlying mechanisms of HE-resistance is necessary. Using advanced ab initio calculations combined with the Monte Carlo approach, we established more realistic atomistic models, i.e., low-energy state of atomic arrangements, of bulk, grain boundary, stacking fault, and surface of model high-entropy alloy, CrMnFeCoNi. Based on the model structures, the thermodynamics and kinetics of hydrogen and water interaction with CrMnFeCoNi alloy, as well as its mechanical properties were studied and compared with reference systems, such as nickel and copper. In addition, we developed a mesoscale computational tool for modeling hydrogen bubble nucleation, accounting for hydrogen diffusion, grain boundary segregation, and surface cleavage. Based on the understanding of an atomistic picture of high-entropy alloy and its interaction with hydrogen, our research provides conditions impeding bubble nucleation and a grain-boundary engineering strategy towards enabling HE-resistant high-entropy alloys with high strength and ductility.
Our project supported Lawrence Livermore National Laboratory mission focus areas in energy and resource security and leveraged Livermore's core competencies in advanced materials and manufacturing and high-performance computing, simulation, and data science. We developed computing codes for studying local ordering in multi-elemental systems and modeling bubble nucleation, and these can be applicable broadly across many Laboratory mission spaces ranging from energy materials, materials degradation, to nuclear waste storage.
Publications, Presentations, and Patents
Kang, S., et al. 2020. "Computational approach to understand properties of high-entropy alloys and hydrogen defects." MSIPP-ESEM consortium, virtual. LLNL-PRES-814040.
Tamm. A., et al. 2021. "Density functional theory study of short-range order in bulk, grain boundary, stacking fault, and surface of CrMnFeCoNi alloy." 2nd World Congress on High Entropy Alloys (HEA 2021), Charlotte, NC. LLNL-ABS- 821445.
Haxhimali, T., et al. 2021. "Multiscale modeling of hydrogen bubble nucleation." 2nd World Congress on High Entropy Alloys (HEA 2021), Charlotte, NC. LLNL-ABS- 821446.
Kang, S., et al. 2021. "Element distribution and hydrogen embrittlement properties in CrMnFeCoNi alloy." Department seminar at Villanova University, virtual. Tracking number: 1042111.