Hydrogen behavior in Al Cr alloys: Synchrotron-based photoelectron microscopy of the rapidly solidified structure

This work reports recent advances in characterization of the composition at submicron length scales of Al-based rapidly solidified alloys, which are correlated to their interactions with hydrogen. The hydrogen desorption kinetics and the evolution of the surface and subsurface structure and chemical state of high-purity Al and Al-3.0 at.% Cr alloy have been studied by thermal desorption analysis and scanning photoelectron microscopy. The alloy foil structure consisted of Cr-rich and Cr-depleted surface regions exhibits Cr segregation beneath the surface. The obtained results reveal how inclusions of aluminum oxide species can become very strong hydrogen traps at the highest temperatures of 600–630 °C, representing irreversible trapping in Al and its alloy. The effect of strong reversible and irreversible hydrogen traps on hydrogen desorption from aluminum alloys is discussed, suggesting that their direct identification in the microstructure provides further insights into hydrogen embrittlement mechanisms for aluminum materials in energy technologies.