Dependence of pop-in behavior of a high-entropy alloy FeCoCrMnNi on tip radius
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Our previous work has established that the dislocation nucleation during the 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 2013 nm were used. It was found that when tip radius is smaller than 638 nm, the pop-in or displacement burst size increases linearly with it, and that when tip radius is larger than 638 nm, the pop—in 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 rationalize the above observations.
This work was mainly conducted during Zhu’s PhD at the University of Tennessee Knoxville. Zhu would like to thank Dr. Nieh from the University of Tennessee Knoxville for his guidance. Startup funds from Wuhan University of Technology under the grant numbers 444-20411183 and 471-40120378 are also deeply acknowledged.
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