1D growth of Cr-rich nanophase induced by hydrogen in high-entropy alloy AlCoCrFeNi2.1

Abstract

• Body-centered cubic phase in cast AlCoCrFeNi 2.1 contains lots of Cr-rich nanophases. • During the hydrogenation process, excess dislocations and vacancies are generated. • Dislocation pile-up and lattice misfit at the phase boundaries favor Cr-segregation. • Hydrogen-induced Cr-segregation near nanophase leads to its one-dimensional growth. One-dimensional (1D) growth of dense Cr-rich nanophase was found in the body-centered cubic (BCC) phase of the eutectic dual-phase high-entropy alloy (HEA) AlCoCrFeNi 2.1 after hydrogen charging (AHC). H atoms diffuse faster and deeper in the BCC, resulting in abundant vacancies and dislocations. The plentiful nanophase particles in the BCC phase before hydrogen charging (BHC) provide nucleation sites for its growth. Cr atoms diffuse faster under the complex interaction of dislocations, vacancies, and H atoms. Furthermore, the dislocations pinned by the nanophase lead to Cr atoms attached to the nanophase segregation. The 1D growth of nanophase shows two growth modes: island-chain fiber and habit-plane whisker.