High entropy alloys (HEAs) are a novel class of materials with great application potential. The HEA used in this study is the so called Cantor alloy [1], consisting of equal fractions of Cr, Mn, Fe, Co and Ni. This CrMnFeCoNi alloy is investigated in depth because it shows promising mechanical properties at very low temperatures [2].
In this investigation, it was tried to influence the behavior of the material through severe plastic deformation (SPD), to be precise high pressure torsion (HPT), and following different heat treatments to examine the evolution of the microstructure. To determine the chemistry of the material after the deformation and aforementioned heat treatments atom probe tomography measurements were performed. Evaluating the crystal structure was done via electron diffraction. Finally to determine the microstructure images in the (S)TEM and the SEM were prepared.
It was found that after HPT deformation the material is nano-crystalline and it has a single phase fcc structure like reported in literature [1,3,4]. After the different heat treatments the formation of precipitates in the size regime of up to several hundreds of nm is observed. The formed particles are either enriched in Cr or Ni/Mn or Fe/Co. When the temperature of the heat treatment is high enough the precipitates dissolve again and a single phase fcc microstructure is reached.

[1] B. Cantor, I.T.H. Chang, P. Knight, A.J.B. Vincent, Microstructural development in equiatomic multicomponent alloys, Mater. Sci. Eng. A. 375–377 (2004) 213–218.
[2] B. Gludovatz, A. Hohenwarter, D. Catoor, E.H. Chang, E.P. George, R.O. Ritchie, A fracture-resistant high-entropy alloy for cryogenic applications, Science. 345 (2014) 1153–1158.
[3] F. Otto, A. Dlouhý, C. Somsen, H. Bei, G. Eggeler, E.P. George, The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy, Acta Mater. 61 (2013) 5743–5755.
[4] F. Otto, Y. Yang, H. Bei, E.P. George, Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys, Acta Mater. 61 (2013) 2628–2638.