Microstructure and texture of heavily cold-rolled and annealed fcc equiatomic medium to high entropy alloys

Abstract

The evolution of microstructure and texture after heavy cold-rolling and annealing was investigated in FCC equiatomic medium to high entropy alloys. For this purpose medium entropy ternary CoFeNi and quaternary CoCrFeNi, and high entropy quinary CoCrFeMnNi alloys were cold-rolled to 90% reduction in thickness and annealed at different temperatures. The ternary alloy showed the development of lamellar microstructure and pure metal type texture after heavy cold-rolling. In contrast, the quaternary and quinary alloys showed heavily fragmented microstructure and brass dominated texture. After annealing, the ternary alloy showed abnormal grain growth at lower annealing temperatures and strengthening of the cube component ({001}<100>) with increasing annealing temperature. In contrast, the quinary and quaternary alloys showed more homogenous grain growth and only minor changes in the volume fraction of different texture components during annealing. The observed differences in the microstructure and texture formation during cold-rolling could be understood considering the differences in the stacking fault energy of the three alloys. On the other hand, the evolution of microstructure and texture of the quarternary and quinary alloys was affected by the sluggish diffusion behavior.