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In order to study chemical complexity-induced lattice distortion in high-entropy alloys, the static Debye-Waller (D-W) factor of NiCoFeMnCr solid solution alloy is measured with low temperature neutron diffraction, ambient X-ray diffraction, and total scattering methods. The static atomic displacement parameter of the multi-element component alloy at 0 K is 0.035-0.041 Å, which is obvious larger than that of element Ni (∼ 0 Å). The atomic pair distance between individual atoms in the alloy investigated with extended X-ray absorption fine structure (EXAFS) measurements indicates that Mn has a slightly larger bond distance (∼ 0.4%) with neighbor atoms than that of others. IMPACT STATEMENT The chemical complexity induced local structural disorder in the high entropy alloy is distinguished from the thermal contribution by the combination of neutron and X-ray techniques.

In this study, the effect of carbon addition the cast and rolled microstructures of Cantor alloy type FeCoCrNiMn high entropy alloys. Both as-cast FeCoCrNiMn and FeCoCrNiMnC0.1 alloys have dendritic microstructure. Small particles, which may be associated carbon addition exist in the dendrite arms in FeCoCrNiMnC0.1 alloy. After homogenization treatment at 1327K for 24 hrs., dendritic structure was completely eliminated after annealing. Dendritic structure was converted to the structure with elongated grains, especially for carbon added FeCoCrNiMnC0.1. The development of elongated grains is associated with the direction of the primary arms in the dendritic structure. Carbides are segregated at the grain boundaries in FeCoCrNiMnC0.1 alloy. It also appears that growth of grains is impeded by the segregation of carbides. It is apparent that the grain boundary precipitates are Cr-rich. Both the strength and ductility of FeCoCrNiMnC0.1 increased over FeCoCrNiMn with the addition of 0.1 wt. % carbon. The increase of ductility in FeCoCrNiMnC0.1 may be caused by the rapid hardening in FeCoCrNiMnC0.1 due to dislocation-solute interaction.