Second phase formation in the CoCrFeNiMn high entropy alloy after recrystallization annealing

There is a strong belief that the CoCrFeNiMn alloy is an example of high entropy alloy with single disordered solid solution structure. Recently it was challenged by the demonstration of second phases in the alloy after low-temperature annealing; however, specific processing conditions (prolonged annealing or severe plastic deformation prior to annealing) were used to cause their formation. In this letter, we report the formation of Cr-rich second phases with tetragonal (sigma phase) and bcc structures in the CoCrFeNiMn alloy after room or cryogenic temperature rolling to 80% strain thickness and further annealing at 600-800 °C for 1 h.