Hydrogen cycling effects on the local order of high entropy alloys

We are currently studying new high entropy alloys as promising solid-state stores for hydrogen. These alloys quickly absorb H at STP conditions forming hydrides and they can desorb H by heating. Despite many similarities, the H absorption capacity is fading during H absorption/desorption cycling for some alloys whereas for others it stabilizes at the first cycle. The reason of such behaviour is not yet known. We hypothesis that this might be due to the developing of short-range ordering by sequential cycling. Moreover, laboratory X-ray diffraction before and after cycling did not allow us to conclude about a possible structural change nor phase segregation. Thus, we propose to study here the local crystal structure in various compositionally complex alloys (five HEAs) as well as its change induced during H absorption/desorption cycling by in situ X-ray total scattering and associated PDF analysis.