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MM: Fachverband Metall- und Materialphysik

MM 31: Topical Session: Hydrogen in Materials: from Storage to Embrittlement V

MM 31.1: Topical Talk

Wednesday, March 20, 2024, 10:15–10:45, C 130

Compositional effects on the hydrogen sorption in refractory high entropy alloys — •Claudia Zlotea and Nayely Pineda-Romero — ICMPE CNRS Thiais France

High entropy alloys represent a novel alloying strategy that can yield exceptional performance properties needed across a variety of technology applications, including hydrogen storage. Examples include high volumetric capacity materials (BCC alloys forming FCC dihydrides) with improved thermodynamics relative to conventional high-capacity metal hydrides (like MgH2), but still further destabilization is needed to reduce operating temperature and increase materials-level capacity. In this presentation, we will show a strategy to effectively destabilize TiVNb-based hydrides by adding small amounts of Al/Mo/Cr. We specifically evaluate the effect of Al/Mo/Cr addition on the phase structure, microstructure, hydrogen absorption and desorption properties. The experiments demonstrate that increasing Al/Mo/Cr content results in a significant hydride destabilization. The change of the local structure as function of chemical composition and hydrogen concentration will be emphasized by total X-ray scattering at synchrotron and related pair distribution function analysis. Moreover, the phase transition during reaction with hydrogen will be highlighted by in situ neutron and synchrotron X-ray diffraction. Finally, hydrogen absorption/desorption cycling properties will be addressed with an emphasis on the structure/microstructure cycle-life stability. The presentation will conclude about possible strategies for the design of high-entropy hydrides targeted for specific hydrogen use cases.

Keywords: hydrogen sorption; high entropy alloys; local structure