In this project, we explore the hydrogen-storage capabilities of quaternary refractory high-entropy alloys (RHEAs) showing transformation-induced plasticity (TRIP) by electro-chemical charging. The initially body-centered cubic (BCC) alloy can be partially transformed into the hexagonal close-packed (HCP) phase upon room temperature straining, allowing to adjust the HCP fraction by the pre-straining conditions. After electro-chemical charging a high fraction of compositionally complex face-centered cubic (FCC) hydrides form in the HCP phase. We employ atomic resolution imaging, electron energy loss spectroscopy (EELS) and in situ
heating in the transmission electron microscope (TEM) to determine the hydride formation sequence, their stability and dissolution mechanisms.