In situ mechanical characterization of CoCrCuFeNi high-entropy alloy micro/nano-pillars for their size-dependent mechanical behavior

Abstract

High entropy alloys (HEAs), as a new kind of alloys with equi-or near equi-atomic alloy compositions, have recently received increased interest, but their mechanical properties at micro-and nanoscales are less studied, which could hinder their structural/functional applications in the small scales. In this work, the mechanical responses of single crystalline FCC-structured CoCrCuFeNi HEAmicro-and nano-pillars were systematically investigated by an in situSEM nanoindenter. The yield strengths of theHEA micro-/nano-pillars under uniaxial compression appear to be size-dependent (with them value of 0.46 in the Hall-Petch law relationship), but less sensitive when compared to typical metal/ alloy micro-and nano-structures (e.g. with themvalues of 0.6-0.9 for FCC metals).We also observed and analyzed the slip systems of the plastically deformed micro-/nano-pillars, and discussed their deformation mechanisms together with the Young's modulus by multiple loading/unloading compressions experiments. Our results could provide useful insights in the design and application of HEAfor functional micro-and nano-devices.