Nanoindentation behavior and cyclic degradation mechanism of BCC phase AlCoCrFeNi high-entropy alloy

QX Tan and B Wang and R Luo and JH Shen and B Gu, APPLIED SURFACE SCIENCE, 687, 162235 (2025).

DOI: 10.1016/j.apsusc.2024.162235

This work investigates the microstructure, dislocation evolution and degradation mechanism of single crystal AlCoCrFeNi high-entropy alloy (HEA) with BCC phase under nanoindentation at different indentation depths, temperatures and cycles. The results reveal that an increase in indentation depth leads to the formation of a dislocation displacement platform within the matrix, accompanied by a transition in dislocation network morphology from symmetrical to isotropic. Strengthening mechanism of AlCoCrFeNi HEA is the synergy between 1/2 <111> dislocations and <100> dislocations. As the ambient temperature increases, temperature-induced transition to disordered structure becomes more pronounced, with a concurrent rise in the fraction of amorphous atoms, which limits the growth and slip of dislocations. As the number of cycles increases, a progressive diminution is observed in the accumulation of high strain atoms and residual depths, which essentially ceases after the 4th cycle. The cyclic degradation mechanism is mainly characterized by localized lattice distortion caused by dislocation pile up and the accumulation of disordered structures induced by stress-induced phase transition.

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