10In high entropy alloys, the number of base alloying elements is increased to at least five and their 11 individual concentrations are rather high in comparison to conventional metallic alloys. This strategy 12 aims at maximization of the configurational part of entropy and stabilization of disordered, single-13 phase solid solutions with simple crystal structure. In the present contribution, a first attempt is 14 presented for the exploration of the phase field of the face centered cubic solid solution in the vicinity 15 of the well-known equimolar composition of CoCrFeMnNi (Cantor alloy) on the basis of 16 combinatorial thin film deposition from sectioned, circular targets by magnetron sputtering. A 17 variation of the chemical composition of the thin films from almost binary systems for substrates 18 (placed on circular positions at the rim of the coated area) towards thin films with an almost equimolar 19 composition (i.e. obtained for samples coated at the center region of the target) was achieved. Crystal 20 structures of the binary thin films were studied and the according lattice parameters of body centered 21 cubic, face centered cubic, hexagonally closed packed and complex cubic (α-Mn prototype) crystal 22 structures are in good accordance with expectations for solid solutions from literature data. The 23 microstructure of the face centered solid solution thin films deposited at the center region of the target 24 was investigated in detail by transmission electron microscopy and atom probe tomography. An ultra-25 fine grained, columnar microstructure was found exhibiting disorder down to atomic length scale. 26Thus, a suitable platform for future investigations of the entire face centered cubic phase field is 27 provided and the strength of the combinatorial thin film approach for the investigation of complex 28 microstructure development in high entropy alloy systems is revealed. 29
