Investigating size dependence in nanovoid-embedded high-entropy-alloy films under biaxial tension

The size dependence of central nanovoid embedded in either monocrystalline or polycrystalline high-entropy-alloy (HEA) films under biaxial tension is investigated in this study. Regarding monocrystalline samples, our attention is paid to the proportional increase in the embedded nanovoid with invariant void volume fraction (VVF). The critical stresses in concerned materials at which dislocations start to emit from void under biaxial tension, in an ascending order, are CoCrFeCuNi < CoCrFeMnNi < metal Ni. Lattice distortion appears to facilitate dislocation emission from the void surface in HEAs, which lowers the critical stress compared with the theoretical model. Regarding polycrystalline samples, the size of both the film and embedded nanovoid is kept invariant, whereas grain size of either periodic hexagonal ones or randomly generated ones is allowed to vary. Apart from the random polycrystalline CoCrFeCuNi, the peak stresses of rest polycrystalline samples obey the reverse Hall-Petch effect. Both monocrystalline and polycrystalline CoCrFeMnNi samples fail due to the coalescence with nucleated secondary voids. For the latter, grain boundaries act as primary sites for secondary void nucleation. Unlike HEAs, polycrystalline Ni samples fail due to intergranular cracking instead of void growth and coalescence.

Automated summary

The size dependence of central nanovoid embedded in high-entropy-alloy films under biaxial tension is investigated. It is found that lattice distortion facilitates dislocation emission from the void surface, leading to a decrease in critical stress. Additionally, the grain size variation affects the peak stress in polycrystalline samples, and the failure mechanism differs between monocrystalline and polycrystalline samples.