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In situ neutron diffraction experiments have been performed to investigate the deformation mechanisms on CoCrFeNi high entropy alloys (HEAs) with various amounts of doped Cu. Lattice strain evolution and diffraction peak analysis were used to derive the stacking fault probability, stacking fault energy, and dislocation densities. Such diffraction analyses indirectly uncovered that a lower degree of Cu doping retained the twinning behavior in undoped CoCrFeNi HEAs, while increasing the Cu content increased the Cu clusterings which suppressed twinning and exhibited prominent dislocation strengthening. These results agree with direct observations by transmission electron microscopy. [ABSTRACT FROM AUTHOR]

To reveal if universal rules may exist in face centered cubic (FCC) concentrated solid solution (CSS) alloys for strength and plastic deformation at room and cryogenic temperatures, we select a FCC CSS superalloy Haynes 188 to demonstrate the deformation mechanisms from atomic to micrometer scales. In FCC CSS alloys, the yield strength (YS) is intrinsically determined by atomic/modulus mismatches and affected extrinsically by grain size; the tensile strength and elongation to fracture (EF) are governed by the plastic process where low stacking fault energy is beneficial. Moreover, almost all CSS alloys show that YS and EF increase simultaneously with the decrease in the temperature. Our findings may expand alloy application and can be used as a design strategy for stronger and tougher alloys. [ABSTRACT FROM AUTHOR]