Decomposition kinetics of carbon-doped FeCoCrNiMn high-entropy alloy at intermediate temperature
(1. School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2. Collaborative Innovation Center for Advanced Ship and Deep-sea Exploration (CISSE), Shanghai Jiao Tong University, Shanghai 200240, China;
3. Shanghai Key Laboratory of High Temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, China)
2. Collaborative Innovation Center for Advanced Ship and Deep-sea Exploration (CISSE), Shanghai Jiao Tong University, Shanghai 200240, China;
3. Shanghai Key Laboratory of High Temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: Phase decomposition kinetics and the corresponding mechanical properties of the severe cold-rolled (SCRed) carbon-doped (1.3 at.%) equimolar FeCoCrNiMn high-entropy alloy (HEA) after being annealed at 500 °C were investigated. This single face-centered cubic (FCC) solid-solution HEA decomposed to M23C6+L10, B2, and σ in chronological order. The formation kinetics of the L10, B2, and σ phases followed the Johnson-Mehl-Avrami- Kolmogorov (JMAK) equation. The yield strength of the HEA was 1520 MPa and increased to 1920 MPa after being annealed at 500 °C for 1 h, as a result of the formation of nanosized M23C6 and L10. Both strength and ductility decreased after 2 d of annealing due to the increase of volume fractions and the coarsening of the M23C6 and L10 precipitates. From 4 to 32 d, the hardness was found to increase, which is ascribed to the rapid formation of the B2 and σ phases. From 32 to 64 d, the hardness increased further to finally reach about HV 760, with the FCC matrix almost exhausted to form the M23C6, L10, B2, and σ phases. The results of this work may serve as a guide for the heat-treatment of carbon-doped HEAs.
Key words: FeCoCrNiMn; high-entropy alloy; decomposition kinetics; mechanical properties; carbon doping