TY - JOUR AU - 장재일 DA - 2015/09 PY - 2015 UR - https://www.cambridge.org/core/journals/journal-of-materials-research/article/nanomechanical-behavior-and-structural-stability-of-a-nanocrystalline-cocrfenimn-highentropy-alloy-processed-by-highpressure-torsion/9E813EE69E261F8D7263C5D1634392AE UR - http://hdl.handle.net/20.500.11754/27383 AB - A CoCrFeNiMn high-entropy alloy (HEA), in the form of a face-centered cubic (fcc) solid solution, was processed by high-pressure torsion (HPT) to produce a nanocrystalline(nc) HEA. Significant grain refinement was achieved from the very early stage of HPT through 1/4 turn and an nc structure with an average grain size of similar to 40 nm was successfully attained after 2 turns. The feasibility of significant microstructural changes was attributed to the occurrence of accelerated atomic diffusivity under the torsional stress during HPT. Nanoindentation experiments showed that the hardness increased significantly in the nc HEA during HPT processing and this was associated with additional grain refinement. The estimated values of the strain-rate sensitivity were maintained reasonably constant from the as-cast condition to the nc alloy after HPT through 2 turns, thereby demonstrating a preservation of plasticity in the HEA. In addition, a calculation of the activation volume suggested that the grain boundaries play an important role in the plastic deformation of the nc HEA where the flow mechanism is consistent with other nc metals. Transmission electron microscopy showed that, unlike conventional fcc nc metals, the nc HEA exhibits excellent microstructural stability under severe stress conditions. PB - CAMBRIDGE UNIV PRESS KW - STRAIN-RATE SENSITIVITY KW - SEVERE PLASTIC-DEFORMATION KW - MECHANICAL-PROPERTIES KW - ACTIVATION VOLUME KW - GRAIN-REFINEMENT KW - ROOM-TEMPERATURE KW - METALS KW - EVOLUTION KW - CU KW - NANOINDENTATION TI - Nanomechanical behavior and structural stability of a nanocrystalline CoCrFeNiMn high-entropy alloy processed by high-pressure torsion IS - 18 VL - 30 DO - 10.1557/jmr.2015.239 T2 - JOURNAL OF MATERIALS RESEARCH ER -