Tensile creep behavior and mechanism of CoCrFeMnNi high entropy alloy

As a potential novel superalloy, the study on the creep of high entropy alloys is of great significance. Equiatomic ratio CoCrFeMnNi with a mass of 6.7 kg was fabricated by vacuum induction levitation melting. Dendrite structure is obtained for as-cast alloy while a homogeneous equiaxed grain structure can be formed after annealing at 1273 K for 6 h. The tensile creep behavior of as-annealed alloy at 773-973 K and 50-340 MPa is systematically studied. Apparent dynamic recovery and recrystallization occur for creep at 973 K while high dislocation density can be observed for creep at 923 K and lower temperatures. Results of EDS analyses on fractured surface, stress exponent and activation energy for steady state creep rate suggest that the creep mechanism should be the dislocation viscous glide dragged by solute Mn at low stresses and low temperatures and be the dislocation climb associated with Mn diffusion at high stresses and high temperatures.