Suppressed Plastic Anisotropy via Sigma-Phase Precipitation in CoCrFeMnNi High-Entropy Alloys

The effect of sigma-phase precipitation on plastic anisotropy of the equiatomic CoCrFeMnNi high-entropy alloy was investigated. Annealing at 700 degrees C after cold-rolling leads to the formation of the Cr-rich sigma phase with a fraction of 2.7%. It is experimentally found that the planar anisotropy ( increment r = -0.16) of the CoCrFeMnNi alloy annealed at 700 degrees C is two times lower than that of the alloy annealed at 800 degrees C ( increment r = -0.35). This observation was further supported by measuring the earing profile of cup specimens after the deep drawing process. The plastic strain ratio, normal anisotropy, and planar anisotropy were also predicted using the visco-plastic self-consistent model. The results indirectly indicated that the reduction of plastic anisotropy in alloy annealed at 700 degrees C can be attributed to the formation of the sigma phase.