Effects of C and La on the Tensile Property and Hot Working Characteristics of CoCrFeMnNi High-Entropy Alloy

Abstract

CoCrFeMnNi high-entropy alloy series were cast by magnetic suspension vacuum melting furnace. They were forged at 1160°C and annealed at different temperatures. Gleeble3800 thermal deformation simulation testing machine was used to conduct thermal compression simulation to research the hot workability of the alloy. The results show that the microstructures of these alloys are made up of solid solution with face-centered-cubic structure and white granular precipitate M23C6. The addition of C and La increases the elongation of CoCrFeMnNi high-entropy alloy forged without annealing by 1.32 times. Annealing deteriorates the tensile properties of these alloys. The constitutive equation and thermal processing diagram of the alloy are established according to the results of thermal simulation. The addition of C and La reduces the flow stress of CoCrFeMnNi high-entropy alloy, but significantly reduces the instability region of thermoplastic deformation. The optimized thermal process parameters are as following: ①CoCrFeMnNi, when the range of the deformation temperature and the strain rate are respectively 900~1040°C and 0.01~0.025s−1, the optimum deformation temperature is 1040~1100°C, and the strain rate is in the range of 0.013~0.033s−1; ②CoCrFeMnNiC0.007La0.0004, when the range of the deformation temperature and the strain rate are respectively 1000~1080°C and 0.31~1s−1, the optimum deformation temperature is 1080~1100°C, and the strain rate is 0.01~0.025s−1.