Precipitation behaviors and mechanical properties of a cold-rolled equiatomic FeCoCrNiMn high entropy alloy after long-time annealing treatment at 500 °C

Abstract

The thermodynamic stability of extensively investigated equiatomic FeCoCrNiMn high entropy alloy has been doubted in recent investigations. In this study, we conducted a long-time annealing treatment on a cold-rolled FeCoCrNiMn alloy at 500 ℃ with the time from 240 to 960 h. The results show that three phases precipitated after a long-time annealing treatment at 500 ℃. The precipitation sequence of these phases starts with two phases (a Cr-rich phase and a NiMn-rich phase) at annealing time ranging from 240 to 720 h, followed by a third FeCo-rich phase at a longer annealing period of 960 h. Besides, the long-time annealing treatment at 500 ℃ results in partial recrystallization of the cold-rolled alloy. The formation of the precipitation affects significantly the mechanical properties of the alloy, including hardness, yield strength and also the ductility.