Decelerated grain growth kinetic and effectiveness of Hall-Petch relationship in a cold-rolled non-equiatomic high entropy alloy

•Grain growth behavior of a non-equiatomic cold-rolled high entropy alloy.•Extremely low grain growth kinetic even at high homologous temperature.•Unexpectedly decreasing trend of the grain growth kinetic with increasing annealing temperature.•Activation of sluggish diffusion and solute drag like effect in whole-solute matrix.•Effectiveness of Hall-Petch relationship and the stability of the matrix during straining. [Display omitted] The present work deals with the grain growth behavior and mechanical properties of a cold-rolled non-equiatomic metastable Fe50Mn30Co10Cr10 high entropy alloy. The bimodal grain size distribution which was developed during isothermal annealing at the temperature range of 750–1050 °C, was gradually annihilated through increasing the annealing time. This was due to the higher capability of fine grains to grow up compared with coarse grains. The obtained grain growth exponents and grain growth activation energies were well higher than those reported for solid solution alloys and also reported for five component CoCrFeMnNi high entropy alloy. The extremely low grain growth kinetics of the experimented alloy even at high homologous temperature was discussed regarding the solute drag like effect of whole-solute matrix in addition to the sluggish diffusion as an intrinsic properties of high entropy alloys. The variation in mechanical properties of the experimented alloy was mainly discussed relying on the effectiveness of Hall-Petch relationship and the stability of the matrix. It was found that the grain boundaries acted as an effective barrier against dislocation motion, and caused postponement of the strain induced transformation leading to an acceptable strength/ductility balance.