Effects of microstructure and vibration parameters on mechanical properties of nanoimprinted FeNiCrCoCu high-entropy alloys

Abstract

Molecular dynamics (MD) simulations are utilized to study the mechanical behavior of FeNiCrCoCu high-entropy alloys (HEA) during nanoimprint lithography with single-crystal, polycrystal, and nano-twinned polycrystal structures. The findings of MD simulations reveal that the microstructure and vibration parameters significantly impact the loading force, elastic recovery ratio, and deformation behavior of FeNiCrCoCu HEA. The imprinting force curve revealed that the maximum loading force is in reduced order with single-crystal, nano-twinned (NT) polycrystal, and polycrystalline structures. With the polycrystalline structure, an inverse Hall-Petch relationship is observed when the grain size varies from 5.1 nm to 9.8 nm. Grain boundary (GB) plays an important role in softening material; the splitting of grains, the migration of the GBs, and grain rotation are the main deformation mechanisms of this region. For NT polycrystals, the stability of material can be enhanced due to the existence of twin boundaries (TB), and the migration of TB is explored near the imprinted region. With polycrystalline structure, the best formability is observed for specimens with a grain size of 9.8 nm, where the average elastic recovery ratio is the smallest, and the forming shape at this grain size is the best. The mold angle of 10° and 20° result in the pattern having a good symmetrical shape, suggesting a better-imprinted shape than with other angles. Moreover, the effect of high-frequency mechanical vibration is analyzed carefully in this study. The results show that the best forming ability is achieved as the vibration amplitude is 3.0 Å. As changing vibration frequencies, the frequency of 50 GHz gives the highest forming ability.