Influence of chemical composition of the surface layer on the nucleation of plasticity in CoCrFeMnNi high-entropy alloys

Abstract

Abstract The role of segregation of chemical elements upon free surfaces in the peculiarities of the plastic deformation mechanisms of thin films of the high-entropy CoCrFeMnNi alloy was clarified using a combined simulation of the Metropolis Monte Carlo and molecular dynamics. Irrespectively of surface orientation and stoichiometric composition of alloy Mn escapes to free surface and Fe goes to the bulk of the films. Ni also enriches the (111) surface while Co content is reduced. It is shown that for different compositions segregation reduces or decreases the elastic limit of the samples. In Co10Cr10Fe30Mn30Ni20 for all considered free surfaces, segregation equally influences the type and volume fraction of the formed defects. In Co30Cr30Fe10Mn10Ni20, they may remain the same or the mechanism of plastic deformation may change drastically in samples with segregation depending on the orientation of the free surface. Despite the redistribution of the volume fractions of various type defects, in general, the main mechanism for the development of plasticity in samples both before and after segregation is the growth of the hcp-bands. Change of defect structure in samples with surface segregation compared to samples with random distribution of elements is not necessary related to change of elastic limit.