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Hydrogen embrittlement behavior of high-entropy alloys

In this project, the hydrogen embrittlement mechanisms in several types of high-entropy alloys (HEAs) have been investigated through combined techniques, e.g., low strain rate tensile testing under in-situ hydrogen charging, thermal desorption spectroscopy (TDS), electron channeling contrast imaging (ECCI) and transmission electron microscope (TEM). The effects of hydrogen on electrochemical properties of HEAs have also been studied.

Metallic materials occupy key roles in providing sustainable engineering and manufacturing solutions to such diverse fields as energy supply, transportation, health, infrastructure and safety. This excellent mechanical behavior can drastically deteriorate when metals are exposed to certain elements. Since 1874 it is understood that the lightest of them all, hydrogen, can be dangerous as it causes catastrophic and unpredictable failure, a phenomenon referred to as hydrogen embrittlement. HEAs are substances that are constructed with equal or nearly equal quantities of five or more metal elements. These alloys are currently the focus of significant attention in materials science and engineering because they have potentially desirable properties. This type of materials could be potentially used for hydrogen environment in the future. Therefore, it is very essential to explore the effect of hydrogen on the anti-hydrogen embrittlement of this type of alloy. According to the basic understanding of the hydrogen embrittlement mechanisms in HEAs, hydrogen interacts with the internal microstructures of HEAs, e.g., vacancies, dislocations, twins and voids. Further, new anti-hydrogen embrittlement HEAs could be designed.

Deformation microstructures near the fracture surfaces of CoCrFeMnNi HEA samples without and with hydrogen. (a) A few deformation induced nanotwins formed in the fractured sample without hydrogen. (b) High density of nanotwins in the fractured sample pre-charged for 72 h at 25 mA·cm-2.

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