Dependence of pop-in behavior of a high-entropy alloy FeCoCrMnNi on tip radius

摘要

Our previous work has established that the dislocation nucleation duringthe onset of plasticity, the so-called pop-in, in face-centered cubic single-phased high-entropy alloy FeCoCrMnNi is controlled by vacancy defects. This implies that the tip radius would affect the pop in behavior as the number of vacancy, the available sites for dislocation nucleation, within the stressed volume is proportional to radius. To verify this in current work, a wide range of nanoindenter tips with radius across from 200 to 2013nm were used. It was found that when tip radius is smaller than 638nm, the pop-in or displacement burst size increases linearly with it, and that when tip radius is larger than 638nm, the popin size became essentially constant. These experimental findings confirm the effect of tip radius on pop-in behavior. A theoretical model based on image force has been developed to rationalizethe above observations.