Tailored precipitation assisted by laser-induced cellular dislocation network structures in Al0.3CoCrFeNi high entropy alloy

Abstract

Cellular dislocation network structures play a critical role in strengthening metals, while their ability to tailor the precipitation of second-phase particles has long been overlooked. Herein, a novel strategy combining laser surface treatment and two-steps annealing is proposed to produce B2 network structures in the as-cast Al0.3CoCrFeNi high-entropy alloy. Cellular dislocation network structures are first introduced in the plates by the laser surface treatment on both sides, then the L12 phase is precipitated on the wall of the dislocation networks by annealing at 700 °C. During second annealing at 800 °C, previously precipitated L12 precursors provide kinetically preferred sites and element segregation for the precipitation of the B2 phase, finally forming dense B2 network structures within the defect-scarce matrix. Dislocations can easily move inside the network structures, and they are blocked by the B2 particles in the wall areas, thus presenting a superior strength-ductility synergy.