Atomic Insight into Nanoindentation Response of Nanotwinned FeCoCrNiCu High Entropy Alloys

FeCoCrNiCu High-entropy alloys (HEAs) exhibit extraordinary mechanical properties and have the capability to withstand extreme temperatures and pressures. Their exceptional attributes make them suitable for diverse applications, from aerospace to chemical industry. We employ atomic-scale simulations to explore the effects of twinning boundary and twinning thickness on the mechanical behavior of nanotwinned FeCoCrNiCu during nanoindentation. The findings suggest that as the twinning thickness decreases within the range of 19.3 Å to 28.9 Å, both twinning partial slips and horizontal twinning partial slips gradually become dominant in governing the plastic behaviors of the nanotwinned FeCoCrNiCu, thereby resulting in an inverse Hall-Petch effect. Remarkably, when the twinning thickness is compressed below 19.3 Å, a shift in the plastic deformation mechanism emerges, triggering the conventional Hall-Petch relation. The observed Hall-Petch behavior in nanotwinned FeCoCrNiCu is attributed to the strengthening effect imparted by the twinning boundaries. Consequently, the twinning boundary play an instrumental role in steering the plastic deformation mechanism of the nanotwinned FeCoCrNiCu when the twinning thickness descends beneath 19.3 Å. This study contributes significant insights towards the design of next-generation high-performance HEAs, underpinning their potential industrial utilization.