THE EFFECT OF THE THERMOMECHANICAL PROCESSING ON THE MICROSTRUCTURE AND HARDNESS OF (Co25Cr15Fe20Ni40)83Al17 HIGH ENTROPY ALLOY

(Co25Cr15Fe20Ni40)83Al17 is a eutectic high entropy alloy (EHEA), which is composed of face centered cubic (FCC) and body centered cubic (BCC) phases. This dual (FCC+BCC) phase mixture provides good ductility and strength combination. In the scope of this study, it was aimed to analyze the effect of mechanical, thermal and thermomechanical processes on the microstructure and hardness of (Co25Cr15Fe20Ni40)83Al17 EHEA, which was produced by the vacuum arc melting and casting method. With this aim, cold and hot rolling as well as different annealing treatments were applied to the as-cast plates. The cold-rolling was performed at room temperature while the hot rolling temperature was varied in between 500-1000℃. The maximum deformation that can be applied was 50% and 60 % after cold and hot rolling, respectively. The limited deformability was attributed to the increased BCC/B2 content in the eutectic phase mixture with the applied deformation. The hardness was increased from 280 HV to 412 HV after 50% cold-rolling. A similar high hardness value (399 HV) was obtained after ~50% deformation at 750℃, indicating that the dynamic recrystallization had no significant effect up to 1000℃.