Effect of Mn and V on structure and mechanical properties of high-entropy alloys based on CoCrFeNi system

Microstructure and mechanical properties of equimolar composition alloys FeCrCoNi, FeCrCoNiV, FeCrCoNiMn and FeCrCoNiMnV were studied in as-solidified and annealed conditions. The FeCrCoNi and FeCrCoNiMn alloys were single-phase FCC solid-solutions in both conditions. However, the FeCrCoNiV and FeCrCoNiMnV alloys consisted of the intermetallic sigma-phase matrix with a tetragonal crystal lattice and precipitates of a disordered FCC phase. The crystal structures of these alloys were found to be not affected by annealing. A number of criteria were considered to explain phase composition of the studied alloys. It was shown that poor compatibility of V with other alloying elements caused significant distortions of FCC solid solution and thus promoted formation of the sigma phase. Tensile and compressive properties of these alloys together with their microhardness were determined. Significant strengthening accompanied by the loss of ductility due to formation of the sigma phase was demonstrated in the V containing alloys. The characteristics of the microstructure formation in the studied alloys were discussed. (C) 2013 Elsevier B.V. All rights reserved.