The effects of refractory elements on mechanical properties in CoCrNiFe concentrated solid solution alloys across different temperatures

Abstract

Mo, W and Re are all important strengthening elements in either single phase solid solution (SS) alloys or the SS phases in precipitation-strengthened Ni/Co-based superalloys, of which the compositions are usually complicated. To directly compare the effects of Mo, W and Re on the mechanical properties of concentrated SS alloys, a model CoCrNiFe concentrated SS alloy as the base and three alloys with 3 at.% Mo, W and Re additions are fabricated and their mechanical properties are examined in both quasi-static tensile and creep tests at room and two high temperatures. Experimental and modeling results demonstrate that at room and low temperatures, the order of strengthening effect is W > Mo > Re, in accordance with solid solution strengthening model and thermal activation analysis. On the other hand, Re can significantly decrease the minimum creep rate at 1273 K, primarily due to the reduced diffusivity as confirmed from the diffusion couple analysis.