Nanoindentation into a dual-phase bicontinuous lamellar high-entropy alloy

IA Alhafez and OR Deluigi and D Tramontina and F Valencia and N Merkert and D Farkas and A Caro and HM Urbassek and EM Bringa, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 37, 1406-1417 (2025).

DOI: 10.1016/j.jmrt.2025.05.257

The plastic response of a dual-phase high-entropy alloy to nanoindentation is studied using molecular dynamics simulation. The sample has a bicontinuous lamellar structure consisting of an equiatomic FeNiCrCo fcc phase and an Al50(FeNiCrCo)50 bcc/B2 phase. Its large size (> 28 million atoms) allows comparison of indentations into an fcc lamella, a bcc lamella and on an fcc/bcc interface. In addition, the lamella thickness of 20-30 nm allows for extensive dislocation plasticity both in the fcc and the bcc phase. We find that the hardness of the alloy at the interphase boundary is not a simple average of the hardness of the lamellae. The plasticity is mostly dislocation controlled, and twinning is relevant only in the fcc phase. Phase transformations do not occur and-in contrast to previous studies-even amorphization is negligible. Dislocation pile-ups are observed in the fcc phase next to the interface. Shear strain is not easily transmitted- in the form of dislocations or stacking faults-across phase boundaries.

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