Hydrogen-induced phase boundary Cr-segregation in high-entropy alloy AlCoCrFeNi2.1

Abstract

We characterized the microstructure of the eutectic dual-phase high-entropy alloy AlCoCrFeNi2.1 after hydrogen charging and found that Cr-segregation appeared at the phase boundaries near the surface of the specimens. Further tests demonstrate that high hydrogen concentration results in larger strain and stress fields near the subsurface. During the hydrogenation process, abundant dislocations and vacancies are generated in the face-centered cubic (FCC) phase and move to the vicinity of phase boundaries. High interfacial energies and lattice misfit at the phase boundaries absorb some dislocations and vacancies resulting in nucleation and recrystallization of the Cr-rich phase. Subsequently, the Cr atoms in the FCC phase diffuse towards the phase boundary driven by the concentration gradient, and the Cr-segregation band forms and widens. Additionally, the width of the Cr-segregation band is limited due to the limitation of the diffusion coefficient and the accumulated width of lattice defects near the phase boundary.